Move origination to use the dialing API and send Stasis messages on dial begin and end.

(closes issue ASTERISK-21549)
Reported by: Matt Jordan

Review: https://reviewboard.asterisk.org/r/2512/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@389053 65c4cc65-6c06-0410-ace0-fbb531ad65f3