Add Bluetooth audio support and a Terminal-based music player

[ggoodale]

This PR adds the following:

• Pipewire, a low-level Linux audio management framework
• BlueZ v5, Bluetooth support for Linux
• cmus, a terminal-based music player for Linux

Pipewire is configured to launch at boot time, owned by the beepy user for ease of use. BlueZ integration is configured and pipewire will auto-switch to a bluetooth audio device when one is connected.

To use:

1. Make sure your chosen bluetooth audio device is in pairing mode.
2. As root, launch bluetoothctl and run the following:

[bluetooth]# scan on

< much console spam detailing detected. Look for the <hex device id> for the device you want to connect to.>

[bluetooth]# scan off
[bluetooth]# trust <hex device id>
[bluetooth]# pair<hex device id>

3. Your bluetooth audio device should now be paired with your Beepy. Restart pipewire:

> sudo /etc/init.d/background/S45pipewire restart

4. as the beepy user, launch cmus:

> cmus

Default shortcuts:

• '5' will launch a file browser in your current directory
• 'q' will quit
• 'x' starts playback
• 'c' pauses playback
• 'v; stops playback

Currently this supports MP3, ogg, and WAV, but cmus could be rebuilt with support for AAC, FLAC, or other audio formats as well. Tested with a pair of Apple bluetooth headphones and a bluetooth speaker I had laying around.

@ardangelo It appears that submodule changes have been swept up in this PR for reasons beyond my limited git-fu. let me know if I need to recreate this PR to exclude them (and how to do that, if you know!)

[ardangelo]

After rebasing on master branch, I was able to pair and play a few seconds of an MP3. It did cut out after a few seconds and then cmus locked up. Could be something with my Bluetooth setup, though.

[ggoodale]

Are you on a Zero W or a Zero 2 W? I only have a 2 to test with, unfortunately.

[ardangelo]

Just got back to this,
Can you rebase on the master branch? Or if you give me write access to the branch I can rebase it.
I'm preparing another release soon.