Series/DataFrame, make decision between full and short __repr__ configurable
Extending pandas.set_printoptions() with two extra arguments: _max_rows_ and _max_columns_.
These two numbers impact `pandas.Series.__repr__()` and `pandas.DataFrame.__repr__()`.
Decision between a short representation or a full one is now configurable. Default values are set to the current ones, so the change is transparent.

When using DataFrames with large number of columns, i got tired of typing `print df.to_string()` all the time :-)

``` python
set_printoptions(precision=None, column_space=None, max_rows=None,
           max_columns=None)
    Alter default behavior of DataFrame.toString

    precision : int
        Floating point output precision
    column_space : int
        Default space for DataFrame columns, defaults to 12
    max_rows : int
    max_columns : int
        max_rows and max_columns are used in __repr__() methods to decide if
        to_string() or info() is used to render an object to a string.
```
