It updates the documentation to separate which parameters are static and
which are changed on each line. Using the latter parameters on plugins which
are only run once per file isn't very sensible.

The documentation for the `FileProcessor` class used `indect_char` while the
class itself uses the more sensible name `indent_char`. This updates both the
docstring as well as the documentation.

Yesterday we released the flake8-polyfill package to help with Flake8
compatibility issues. This adds documentation to Flake8 to help people
use that and to guide them towards it.

When calling `add_option` it returns an `Option` object which can return the
primary name of the option via `get_opt_name`. This should be used primarily
in the cross compatible implementation so that the order of parameters does
not matter.

This should make the contents clearer