Exoplayer activity for app - support remote control

[sentinelweb]

• [x] make exoplayer activity with player controls
• [x] setup remote launch
• [x] volume controls
• [ ] try to launch app player on second screen
• [ ] setup cuercast controls in hub
• [ ] play controls for hub - bind to CastController
• [ ] animations to show/hide player controls
• [ ] save state (ordering at least) in filebrowser