Fix validation error type `PR08` and check in CI
#### Problem description
In order to have a continuous check by the CI on validation error `PR08` (Parameter description should start with a capital letter), fixing them in the code base enables the addition to the CI for automated testing in the future.

`PR08` has 156 occurrences (see [overview of the errors](https://gist.github.com/198cfa552c727d71bd7360fda66fdbb4)), including:


method | file | file_line | github_link
-- | -- | -- | --
pandas.Timestamp.ceil | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.day_name | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.floor | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.fromordinal | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.month_name | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.round | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.tz_localize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Period.to_timestamp | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.DataFrame.insert | pandas/core/frame.py | 3434.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L3434
pandas.DataFrame.apply | pandas/core/frame.py | 6284.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L6284
pandas.DataFrame.pipe | pandas/core/generic.py | 4924.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L4924
pandas.DataFrame.corr | pandas/core/frame.py | 6960.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L6960
pandas.DataFrame.corrwith | pandas/core/frame.py | 7151.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L7151
pandas.DataFrame.rank | pandas/core/generic.py | 8287.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L8287
pandas.DataFrame.drop_duplicates | pandas/core/frame.py | 4579.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L4579
pandas.DataFrame.duplicated | pandas/core/frame.py | 4614.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L4614
pandas.DataFrame.idxmax | pandas/core/frame.py | 7564.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L7564
pandas.DataFrame.idxmin | pandas/core/frame.py | 7528.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L7528
pandas.DataFrame.rename | pandas/util/_decorators.py | 3922.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/util/_decorators.py#L3922
pandas.DataFrame.fillna | pandas/core/frame.py | 4007.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L4007
pandas.DataFrame.unstack | pandas/core/frame.py | 5905.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L5905
pandas.DataFrame.from_csv | pandas/core/frame.py | 1838.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L1838
pandas.DataFrame.to_feather | pandas/core/frame.py | 2083.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L2083
pandas.DataFrame.to_msgpack | pandas/core/generic.py | 2380.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L2380
pandas.DataFrame.to_clipboard | pandas/core/generic.py | 2596.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L2596
pandas.merge_ordered | pandas/core/reshape/merge.py | 132.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/reshape/merge.py#L132
pandas.merge_asof | pandas/core/reshape/merge.py | 236.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/reshape/merge.py#L236
pandas.to_numeric | pandas/core/tools/numeric.py | 14.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/tools/numeric.py#L14
pandas.to_datetime | pandas/core/tools/datetimes.py | 401.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/tools/datetimes.py#L401
pandas.to_timedelta | pandas/core/tools/timedeltas.py | 18.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/tools/timedeltas.py#L18
... | ... | ... | ...
pandas.Series.rename | pandas/core/series.py | 3726.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/series.py#L3726
pandas.Series.fillna | pandas/core/series.py | 3893.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/series.py#L3893
pandas.Series.reorder_levels | pandas/core/series.py | 3301.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/series.py#L3301
pandas.Series.dt.tz_localize | pandas/core/accessor.py | 94.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/accessor.py#L94
pandas.Series.dt.round | pandas/core/accessor.py | 94.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/accessor.py#L94
pandas.Series.dt.floor | pandas/core/accessor.py | 94.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/accessor.py#L94
pandas.Series.dt.ceil | pandas/core/accessor.py | 94.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/accessor.py#L94
pandas.Series.str.findall | pandas/core/strings.py | 1755.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/strings.py#L1755
pandas.Series.str.match | pandas/core/strings.py | 2526.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/strings.py#L2526
pandas.Series.str.replace | pandas/core/strings.py | 2531.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/strings.py#L2531
pandas.Series.cat.rename_categories | pandas/core/accessor.py | 94.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/accessor.py#L94
pandas.Series.hist | pandas/plotting/_core.py | 2418.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/plotting/_core.py#L2418
pandas.Series.to_msgpack | pandas/core/generic.py | 2380.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L2380
pandas.Series.to_clipboard | pandas/core/generic.py | 2596.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L2596
pandas.io.formats.style.Styler | pandas/io/formats/style.py | 55.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/io/formats/style.py#L55
pandas.io.formats.style.Styler.apply | pandas/io/formats/style.py | 565.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/io/formats/style.py#L565
pandas.io.formats.style.Styler.applymap | pandas/io/formats/style.py | 623.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/io/formats/style.py#L623
pandas.io.formats.style.Styler.where | pandas/io/formats/style.py | 650.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/io/formats/style.py#L650
pandas.io.formats.style.Styler.set_properties | pandas/io/formats/style.py | 987.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/io/formats/style.py#L987
pandas.io.formats.style.Styler.highlight_max | pandas/io/formats/style.py | 1143.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/io/formats/style.py#L1143
pandas.io.formats.style.Styler.highlight_min | pandas/io/formats/style.py | 1163.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/io/formats/style.py#L1163
pandas.io.formats.style.Styler.background_gradient | pandas/io/formats/style.py | 881.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/io/formats/style.py#L881
pandas.io.formats.style.Styler.use | pandas/io/formats/style.py | 742.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/io/formats/style.py#L742
pandas.core.window.Rolling.apply | pandas/core/window.py | 1699.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/window.py#L1699
pandas.core.window.Expanding.apply | pandas/core/window.py | 1972.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/window.py#L1972
pandas.Panel.fillna | pandas/core/panel.py | 1288.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/panel.py#L1288
pandas.Panel.fromDict | pandas/core/panel.py | 243.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/panel.py#L243
pandas.Panel.pipe | pandas/core/generic.py | 4924.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L4924
pandas.Panel.rank | pandas/core/generic.py | 8287.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L8287
pandas.Panel.to_msgpack | pandas/core/generic.py | 2380.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L2380


Todo:

* [ ]   get rid of the errors in the code base
* [ ]   update the `code_check.sh` script to take into account the `SS02` type of errors