Refactoring part two

Removed obsolete Play message
Implemented listeners for audio chunks, buffer requests and audio offers
Implemented a BufferRequest Thread which will keep requesting new chunks until the buffer is full
Implemented a Buffer Printer for debugging purposes
Implemented a GStreamer player
Implemented a Buffer Pump, pumping buffer chunks to the GStreamer outputstream
Implemented a MusicPlayer which will start all threads for succesfull remote play

Still not enough tests, since I copied and refactored most of the old work...