[PyQt] Updated PyQt Documents - Feedback Please

[Phil Thompson]

I've made a new release of the PyQt documentation at...

https://pyqt.readthedocs.io

This is the first stage of creating complete PyQt5 documentation (similar to what was done with the PyQt4 documentation).

The documentation is created from 4 sources:

- "static" text files
- .sip files that provide the objects (modules, classes, enums etc) being documented with hooks
  for "description files"
- the Qt source code which provide the initial content of the description files
- the description files which will be updated over time (a long time!) to become more Pythonic
  as required.

The system is designed so that it can be updated with new PyQt and Qt releases without losing any user-written changes to the description files.

For the moment the description files are just stubs (lots of TODOs) because I wanted feedback on the overall structure before populating it from the Qt documentation.

There are lots of outstanding issues that will be addressed over time. For example, nested classes are only referenced from the class index (mainly an issue for the classes that implement enum flags).

Any feedback and suggestions for improvement are welcome.

Phil