Fix the breakage earlier.

And now for a more reasonable commit message:

- Automatically infers the internal name of a BAPS code.
- Remove the manually defined BAPS code names in the response structures.
Fix break when a response structure doesn't exist.
Implement deletion of playlist items by driver.

This required changing CompositeModelObject child deletion to be
implementation-specific, because for some silly reason Array#delete takes an
object and Hash#delete takes a key.  Grr Ruby...