Adding ability for GHPRB to specify a whitelist of branches that should be tested.  If you specify branches for this whitelist, then only pull requests destin
ed for those branches will be tested.
reverted the replacement of bindJSON instead of specific variable assignments in GhrpbTrigger's configure method, as this was the problem for why we couldn't save global settings.  I've realized that this wasn't needed for the binding to work properly for repeatable fields, in particular for the whitelist target branch's repeatable fields.
Merge pull request #24 from rsennewald/multibranch-whitelist

Multibranch whitelist
Merge remote-tracking branch 'jenkinsci/master'