Channels First with URY Rapid: A Practical Pull Request Using GitHub

* Switch from separate `players` and `playlists` sets to one single `channels` set with channels having a `player` and `playlist` object.  This undoes a change made way back when, as it turns out the 'old' approach makes infinitely more sense for BAPS-a-like playout systems.
* Create a new `FakePlayoutService` example service, mainly so I can test playout model stuff is working properly.
* Improve the API inspector style to look a bit more 
imitation Material Design
 modern and clean.
* Bump API version to 0.5.0.  Not that the API version matters much yet anyway.