Contingent Pings

Add the ability for specified @mentions to be REQUIRED or EXCLUDED in pings that go out.

Examples:
“Any @apex / @preadator peeps =@here wanting to clout up?”
-Will ping every member with the @apex and @predator roles so long are also online.

“=@volunteers =@west Thank you all for a great show!”
-Pings only those who possess both mentoned rolls, not anyone with just one or the other.

“The time has come for Classic Onyxia, @raiders, except for !@leeroy. No one has time for that.”
-Pings everyone in @raiders except for you know who.