DOC: HDFStore documentation needs listing all methods
#### Problem description

The docs (https://pandas.pydata.org/pandas-docs/stable/api.html#hdfstore-pytables-hdf5) doesn't make any mention of ***HDFStore*** methods like `.get_storer`, which I found quite useful for finding number of records without loading the whole file to memory, but I don't see any documentation of it although it pops up in sample code in Cookbook and IOtools pages. 

I am bumping into these methods only on forums, and am not able to find official documentation about them. I found a bigger listing of available methods here: https://stackoverflow.com/a/37986144/4355695 Copying them below for posterity sake. Even the poster there has only linked to the Cookbook page as docs.

Also, there needs to be disambiguation about what works for fixed format and what works for table format. Many code examples are showing table-specific commands and not specifying that this won't work if your data was originally stored in fixed format. The default format in [`pd.to_hdf()`](https://pandas-docs.github.io/pandas-docs-travis/generated/pandas.DataFrame.to_hdf.html) method is `fixed` . Again, this `.to_hdf` method too is not listed under the main HDF5 part of the docs, [`API > Input/Output > HDFStore: PyTables (HDF5)`](https://pandas.pydata.org/pandas-docs/stable/api.html#hdfstore-pytables-hdf5). But we find it under  [`Serialization / IO / Conversion`](https://pandas.pydata.org/pandas-docs/stable/api.html#id12) under Series and DataFrame sections. And I'm not sure how it differs from [HDFStore.put](https://pandas.pydata.org/pandas-docs/stable/generated/pandas.HDFStore.put.html#pandas.HDFStore.put).

Then, `HDFStore.append` will store in table format and will work with existing objects only if they are stored in table formats. But my project's data already got all stored in the default fixed format and now I can't use `append` on them. Also, I want to find out if it's possible to get the listing of columns without loading the whole file like it was with `.get_storer`. But it seems like that too is only available for table format.

```
store = pd.HDFStore('h5File.h5')

store.append_to_multiple
store.close
store.copy
store.create_table_index
store.filename
store.flush
store.get
store.get_node
store.get_storer
store.groups
store.is_open
store.items
store.iteritems
store.keys
store.open
store.put
store.remove
store.root
store.select
store.select_as_coordinates
store.select_as_multiple
store.select_column
```

#### Expected Output
- Documentation of each method/function possible with ***HDFStore***. Possibly a separate page for HDFStore. 
- Specifying what works for the default fixed format and what works for table format.
- Specifying which method loads the whole object into memory and which method doesn't.
- Mentioning of similar methods in each other's docs (like: pd.to_hdf and HDFStore.put ought to mention each other and specify the differences if any)

#### Output of ``pd.show_versions()``

<details>
INSTALLED VERSIONS
------------------
commit: None
python: 3.5.2.final.0
python-bits: 32
OS: Linux
OS-release: 4.13.0-41-generic
machine: i686
processor: i686
byteorder: little
LC_ALL: None
LANG: en_IN
LOCALE: en_IN.ISO8859-1

pandas: 0.22.0
pytest: None
pip: 10.0.1
setuptools: 20.7.0
Cython: 0.27.3
numpy: 1.13.3
scipy: None
pyarrow: None
xarray: None
IPython: 6.2.1
sphinx: None
patsy: None
dateutil: 2.6.1
pytz: 2017.3
blosc: None
bottleneck: None
tables: 3.4.3
numexpr: 2.6.4
feather: None
matplotlib: None
openpyxl: 2.5.3
xlrd: 1.1.0
xlwt: None
xlsxwriter: None
lxml: 3.5.0
bs4: 4.6.0
html5lib: 1.0.1
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
</details>
