Optional different streaming url

[lucasreiners]

In my setup, I am hosting tvheadend and antennas in a docker network. As Plex is not part of this network, I need different URLs for antennas for fetching the channels and for Plex for accessing the actuals streams.

Other than that, I fixed the TUNER_COUNT was not parsed as int from the environment variables, resulting in antennas delivering the tuner count as string, resulting in Plex interpreting it in 50 available tuners

[jfarseneau]

That's awesome, thank you! I've done a bit of refactoring to the code, so I'll tweak your branch a bit and fold in your changes.