Updated some Phoenix documentation:

- Added RichTextCtrl overview;
- Updated `index.rst` to include richtext and webkit packages;
- Added a bunch of converted samples from C++ to Python.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxPython/Phoenix/trunk@75524 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775