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: http://svn.asterisk.org/svn/asterisk/trunk@390901 f38db490-d61c-443f-a65b-d21fe96a405b