Replaced references to unittest with pytest

The developer testing documentation became outdated with the move to
pytest. Therefore, old test examples using the unittest framework were
removed and replaced with an example of using the pyunit framework.

Close #467
Related #420
Related #566
Add tip for Windows install to Quick Start guide

An error may be encountered with the Windows
install of GStreamer by OSSBuild. This can be
solved by copying over some files and deleting
another. The required information is now
provided in the Quick Start guide