Pysdrweb

Restructuring code and adding typing annotations.

HLS Streaming should now work. It should also work with python versions up to
3.12.

Added optional MP3 support; can now use:

pip install pysdrweb[mp3]

to install pysdrweb with MP3 support. This uses the LAME library, which may
be subject to GPL so it is bundled as an optional package.

First version after working out a few bugs with the package server.