Python 3.9 fixups

[asheplyakov]

As of now CHIRP fails to start with Python 3.9:

• Complains about missing importlib_resources module (although importlib is available as a part of the standard library)
• Application icon and stock configs can't be found (since chirp.share is not a proper python package)

With this patchset I can use CHIRP with Python 3.9.