Resolve issues in ConfBridge regarding marked, waitmarked, and unmarked users

Resolve issues in ConfBridge regarding marked, waitmarked, and unmarked users

Thank's to Neil Tallim (flan)'s tireless testing, issue reporting, and patches
it became clear that app_confbridge had some complex logic in how it handled
interactions between marked, waitmarked, and unmarked users.  In particular,
there were some areas in which the interactions between the users resulted
in inconsistent behavior, and app_confbridge was missing logic in how to handle
some corner cases.  Some areas included:
 * Poor handling of mixing unmarked and waitmarked users
 * Inconsistencies in how MOH and muting was applied to various users
 * Handling of various announcements for different user profile options
flan's patches seem to fix the various issues, but highlighted how hard the
code could be to maintain.  In an attempt to make things easier to maintain and
to more fully enumerate the various cases that exist, this patch breaks up the
logic into a state machine-like setup.

Please note that the various state transitioned are documented on the Asterisk
wiki:

https://wiki.asterisk.org/wiki/display/AST/Confbridge+state+changes

Review: //https://reviewboard.asterisk.org/r/2072/

Note that for the following issues, mjordan uploaded the patch, although it
was written by twilson.  Any contributor license discrepency is due to that.

(closes issue ASTERISK-19562)
Reported by: flan
Tested by: flan, mjordan, jrose
patches:
  bugASTERISK-19562_ASTERISK-19726_ASTERISK-20181.patch uploaded by twilson (license 6283)

(closes issue ASTERISK-19726)
Reported by: flan
Tested by: flan
patches:
  bugASTERISK-19562_ASTERISK-19726_ASTERISK-20181.patch uploaded by twilson (license 6283)

(closes issue ASTERISK-20181)
Reported by: Jonathan White
Tested by: Jonathan White
patches:
  bugASTERISK-19562_ASTERISK-19726_ASTERISK-20181.patch uploaded by twilson (license 6283)
........

Merged revisions 374652 from http://svn.asterisk.org/svn/asterisk/branches/10

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@374657 65c4cc65-6c06-0410-ace0-fbb531ad65f3