Added callback.
Returns to REST client after originate succeed, not waiting for answer
anymore.
Added some TODOs and FIXMEs.
Clean code and revised API interface.
Hangup if callee not answered.
Clean code and revised API interface.
Merge branch 'feature/callback' into stable
feature/outbound: added status API interface.
Added broadcast app. start/stop/status API tested.
changed broadcast task media field name to "media_id".
do no return server pid to user.
Added cb_broadcast module.
Added outbound/broadcast whapps to system_config to let
whapps_controller to start them automatically.
Added scheduler support.
Added mnesia related funs.
Added scheduler support.
Fixed bug, call_event works for bowout b-leg now.
Added tasklog and partylog.
Fixed bug in broadcast json schema.
Added listing_tasklog_* and listing_partylog_* views.
Fixed bug in conference json, to allow empty numbers  array.
This's kazoo's bug, try to merge to upstream later.