Seperate setActiveTrack from request DJ

Flow is now as follows:
- user requests to DJ (requestDJ)
- server adds them to the DJ list and tells users (newDJ)
- server tells users who the active DJ is (setActiveDJ)
- active dj tells server what their track is (setActiveTrack)
- server relays that to users (setActiveTrack)
- active DJ and users start peer connections with eachother (todo)
- active DJ plays track and streams it to peers (todo)