Add a convenience method for starting the client.

In addition, some stylistic changes, nothing major.
Move server app.

This will break things that will be fixed in the next commit.

There may have been other changes to the server app, git diff is being very
unco-operative in telling me what.
Allow channel number customisation on the model.

There is also now a new method `player` which returns a channel's player, in
a slight attempt at Law of Demeter.
Mountain of unrelated main changes.
Use config YAML for configuring the server.
Add a model method for setting player state.

More Law of Demeter for you.
Add direct method for loading a player.
Big huge dump of HTML work.

Trying to make a developer-friendly API inspector that'll represent
the BRA API in a readable but not user-ready state.
Another unprincipled dump
Move channel state style to top level.
Remove brackets.
Move player state to a separate view.
Add in/out link styling.
Add in/out links.
Tonight is not a good night for proper version control.
Allow the API root to be specified in the config.
De-hardcode the URL root.
Move some URLs to models.
And some more URLs...
Some Rubocop fixes.