Docs

[matperc]

Based on the work in #167, we can extract documentation for functions and function arguments.

TODO:

• [ ] Add docstring to __init__() for classes
• [x] Fix wrapped functions
• [x] Fix symbol (signal and property tags) with same name of functions (Like Gtk.Widget.show, shows the documentation for the signal and not the function)
• [x] Add documentation for virtual functions (do_xxx)
• [x] Add documentation to properties

Closes #76