[Boombox] added getters for providers and playlist
[ProviderProcessor] clean up after runloop
[Boombox] fixed algorithm for determining hasNext
[Boombox] queue next provider on buffer completion
[AudioDataProvider] added new getters
[ProxyServer] added support for Content-Length
[Boombox] fixed issues with queueing next media player (see desc)

When determining the next provider use, it was being derived from the provider at the current playlist cursor instead of the provider for the tail media player