Fix type retrieval when doc is present.
Starting the coverage of GWeather.

Add required GIR file and module.
Add public API stubs.
Coverage of classes and functions of GWeather.

Add the necessary code to add the coverage of several classes and
functions. Add also some overriders to to cover some methods that
need to be overriden to handle out parameters.
Add weather info example.

Add an example code to demonstrate how to use the weather package
in a simple program to retrieve a bunch of information.
Fix the GWeatherInfoOverride JNI side.