Remove dead code.
Remove model name override.
Rename find_resource to find_url.

This is a more descriptive and terser name; the other X_resource functions will
be changing too soon.
Remove name dependency on playlist view.
Remove channel name alias.
Continue verb renaming.
Fix pretty much everything.

The URL traversal has been redone so that it throws a fit if given a bad URL,
as you'd expect.

URL traversal now works without a trailing /, too.

Some other fixes have now made PUTting player state actually work, though there
are a few bugs that need ironing out.
Add function for retrieving pvar channelID.
Validate item type on PUT, allow nil.
Handle BAPS player states properly.

BAPS interprets a PLAY while PAUSEd as an instruction to return the position
marker to 0 before resuming play (the correct command to unpause is PAUSE), so
some jiggling of the SetPlayerState command was necessary to make this work.

SetPlayerState now expects a from-state as well as a to-state.

Channel commands now operate on channel IDs, not model objects.

Pausing a stopped channel no longer works (it doesn't make any sense!).