Adding Some More Manager Events To ConfBridge

Currently, ConfBridge does not send manager events for ConfbridgeMute,
ConfbridgeUnmute, ConfbridgeStartRecord and ConfbridgeStopRecord.  This patch
adds these events to the manager.

The reporter's patch moves some other events up to the beginning of the file.

The patch being committed is based on the patch contributed from the reporter of
this issue.  I have made a lot of modifications to the patch in order for it to
fit in better with what we currently are doing in the code when it comes to
manager events.  I also made a few changes to the <see-also> elements on some of
the events.

(closes issue ASTERISK-20827)
Reported by: Clint Davis
Tested by: Clint Davis, Michael L. Young
Patches:
    20827.diff uploaded by Clint Davis (license 6453)
    asterisk-20827-confbridge-events.diff uploaded by 
                                                 Michael L. Young (license 5026)

Review: https://reviewboard.asterisk.org/r/2309/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@381256 65c4cc65-6c06-0410-ace0-fbb531ad65f3