added several new partials and controllers for entertainment section + added onkyo addon support for back-end.

Routes:
[GET] /api/v0/addon/onkyo/group            //list of command groups
[GET] /api/v0/addon/onkyo/group/:group      //list of commands in group
[PUT] /api/v0/addon/onkyo/:group/:command   //execute command
[PUT] /api/v0/addon/onkyo/discover   //discover onkyo receiver
[PUT] /api/v0/addon/onkyo/power/:state   // set  on|off -state
[PUT] /api/v0/addon/onkyo/volume/:state   // set  volume up|down|mute|unmute

[PUT] /api/v0/entertainment/audio/power/:state   // set on|off -state
[PUT] /api/v0/entertainment/audio/volume/:state   // set volume up|down|mute|unmute