DOC: closes gh6838. Breakout options.rst from basics.rst

closes #6838. 
closes #3104 
Breakout "options" section for docs, heavily using info already in ``basics.rst``. Expands examples, and turns ``describe_options`` into a table.
you can make links to the docstring page of these so ``` ``get_option`` ``` -> `` :func:`~pandas.get_option` ``