Fix some typos.
Forgot to pass registrar to component creator.
Remove accidental @parent indirection.
Fix typo with player_url call.
And forgot a (response) elsewhere too.
And yet another (response) missed off.
Specify handler target for #marker.
And make it pass.
Factor out #run in the playback handlers.
Use def_targets for consistency.
Add no-change ignoring clauses.
Unfinished heavy refactoring of handlers.
Convert BAPS requester to use handler set.
ARGH LOTS OF HALF-BROKEN REFACTORING
Make System response handlers use new style.
Remove response from channel URLs arguments.
Change playlist response handlers to new style.
New style for Loaders, too.
Use the component creator for making markers, too.

This normalises the handler targets used in bra.
Remove unnecessary debug p.