.net package refactor, PlaybarFragment, AudioPlayerService

This commit contains a few things:

I moved the network related stuff into the .net package (including the new messages just added)

I added a fragment for the play bar.  I don't believe it's finished, but I'd like to get this into the main line so Elizabeth can start playing with placement/look and feel.

AudioPlayerService and SingleFIleAudioPlayer, to play sounds.

This also contains some hacked bluetooth code, but I'm working on rewriting that whole piece, to fix it once and for all.