Manager: Add missing fields and documentation for CoreShowChannels

This corrects some issues introduced in the responses to the
CoreShowChannels AMI command as well as adding documentation for the
responses. The command in Asterisk 12 was missing the following fields:
Duration, Application, ApplicationData, and BridgedChannel and
BridgedUniqueID (replaced with BridgeId).

ASTERISK-24262 #close
Reported by: Mitch Claborn
Review: https://reviewboard.asterisk.org/r/4040/
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Merged revisions 424423 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/13@424424 65c4cc65-6c06-0410-ace0-fbb531ad65f3