Make app_queue AMI events more consistent. Give Join/Leave more useful names.

This also removes the eventwhencalled and eventmemberstatus configuration
options.  These events can just be filtered via manager.conf blacklists.

(closes issue ASTERISK-21469)
Review: https://reviewboard.asterisk.org/r/2586/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@390901 65c4cc65-6c06-0410-ace0-fbb531ad65f3