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: http://svn.asterisk.org/svn/asterisk/trunk@389053 f38db490-d61c-443f-a65b-d21fe96a405b