Add applications JabberJoin, JabberLeave, JabberSendGroup for XMPP groupchat

(closes issue #14352)
Reported by: fiddur
Patches: 
      trunk-14352-2.diff uploaded by phsultan (license 73)
Tested by: fiddur


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@233468 65c4cc65-6c06-0410-ace0-fbb531ad65f3