added section for using Python logging module

[nnathan]

I really like the Python extension pattern docs. This is something I together to demonstrate how to log in an extension.

It is missing a few things:

1. Using logging module as a library requires adding a NullHandler to the logger object incase the application has yet been configured for logging.
2. A logging function which can use python parsed strings and objects for logging in Python aspects (instead of just C).

This logging system has been implemented here.

The documentation is in draft mode and I haven't actually been able to verify the output in a browser yet, but I created the PR first to see if this is something you may want to include, and if you had any thoughts on how I could improve it.

[nnathan]

Bump. Just seeing if you had a chance to see this yet.