Some refactoring on messaging, opened up for multiple users of Messenger
class and centralized handling of request id and pending messages
A bunch of audio endpoint management stuff (work in progress)
Merge branch 'devel' of https://github.com/jderehag/spotifyserver into devel

Conflicts:
	common/MediaInterface/MediaInterface.h
	common/Platform/AudioEndpoints/AudioEndpoint.h
	common/Platform/AudioEndpoints/AudioEndpointRemote.cpp
	common/Platform/AudioEndpoints/AudioEndpointRemote.h
	common/Platform/Socket/Linux/LinuxSocket.cpp
	common/Platform/Socket/Socket.h
	src/ClientHandler/Client.cpp
	src/LibSpotifyIf/LibSpotifyIf.cpp
	src/LibSpotifyIf/LibSpotifyIf.h
Merge branch 'devel' of https://github.com/jderehag/spotifyserver into devel

Conflicts:
	common/Platform/AudioEndpoints/AudioEndpointRemote.cpp
	common/Platform/AudioEndpoints/AudioEndpointRemote.h
	src/ClientHandler/Client.cpp
	src/TestApp/RemoteMediaInterface.h
Some code to try to make everything work after the merges