Remove user supplied regexes as a feature, comma delimit them now

Users of the IRC hook have been able to previously filter branch notification behavior by providing regexes. Since these are user supplied there's crazy ways of constructing regexes that basically eat tons of CPU time analyzing strings. This moves away from the regex supplied by users in favor of a comma delimited list of branch names that must be included.

I'm going to turn this on and see who contacts us via support. I think it's a more reliable approach than the user provided regexes.