Massively clean up app_queue.

This essentially makes app_queue usable again. From reviewboard:

* Reporting of transfers and call completion is done by creating stasis 
  subscriptions and listening for specific events in order to determine
  when the call is finished (either via a transfer or hangup).
* Dial end messages have been added where they were previously missing.
* Queue stats are properly being updated again once calls have finished.
* AgentComplete stasis messages and AMI events are now occurring again.
* Mixmonitor starting has been factored into its own function and uses the
  Mixmonitor API now instead of using ast_pbx_run()

In addition to the changes in app_queue, there are several supplementary changes as well:

* Queue logging now differentiates between attended and blind transfers. A
  note about this is in the CHANGES file.
* Local channel optimization events now report more information. This
  includes which of the two local channels involved is the destination of
  the optimization, the channel that is replacing the destination local channel,
  and an identifier so that begin and end events can be matched to each other.
  The end events are now sent whether the optimization was successful or not and
  includes an indicator of whether the optimization was successful.
* Changes were made to features and bridging_basic so that additional flags may
  be set on a bridge. This is necessary because the queue requires that its
  bridge only allows move-swap local channel optimizations into the bridge.

(closes issue ASTERISK-21517)
Reported by Matt Jordan

(closes issue ASTERISK-21943)
Reported by Matt Jordan

Review: https://reviewboard.asterisk.org/r/2694



git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@397451 f38db490-d61c-443f-a65b-d21fe96a405b