Confbridge: Fix ConfbridgeKick AMI documentation

This adds documentation for the "all" channel option for the
ConfbridgeKick AMI action and adjusts AMI responses accordingly.

(issue ASTERISK-23282)
Reported by: Dorian Logan
........

Merged revisions 412730 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@412731 65c4cc65-6c06-0410-ace0-fbb531ad65f3