Filter channels used as internal mechanisms

This adds new flags to the channel tech properties that flag it as
different types of implementation detail used exclusively to provide a
feature. Examples of channels that would have these flags include the
announcement and recording channels used by confbridge which are the
only two marked as such by this patch.

Review: https://reviewboard.asterisk.org/r/2633/
(closes issue ASTERISK-21873)


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@394808 f38db490-d61c-443f-a65b-d21fe96a405b
ARI: Bridge Playback, Bridge Record

Adds a new channel driver for creating channels for specific purposes
in bridges, primarily to act as either recorders or announcers. Adds
ARI commands for playing announcements to ever participant in a bridge
as well as for recording a bridge. This patch also includes some
documentation/reponse fixes to related ARI models such as playback
controls.

(closes issue ASTERISK-21592)
Reported by: Matt Jordan

(closes issue ASTERISK-21593)
Reported by: Matt Jordan

Review: https://reviewboard.asterisk.org/r/2670/


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@394809 f38db490-d61c-443f-a65b-d21fe96a405b
ARI: MOH start and stop for a channel

(issue ASTERISK-21974)
Reported by: Matt Jordan
Review: https://reviewboard.asterisk.org/r/2680/


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@394810 f38db490-d61c-443f-a65b-d21fe96a405b