Revert "IRCContact use the DATA API"
Merge pull request #1332 from delanne/revert-1323-IRCContact

Revert "IRCContact use the DATA API"
Fix addBuildsetForSourceStampsWithDefaults
 - project is a mandatory parameters of findSourceStampId. So set it to '' by default.
   addBuildsetForChanges does the same thing when a codebase has no changes. (See schedulers/base.py line 249)