set up jobs to handle building from PRs

    "revision" : {
        "HEAD" : "bfe76fb3f3c34d68b873d0acf715e2145e4cb805",
        "currentBranch" : "HEAD",
        "knownReferences" : [{
            "name" : "origin",
            "url" : "git://github.com/jbosstools/jbosstools-build-sites.git",
            "ref" : "pr/221/merge"
        }]
    },

#Fri Feb 05 16:42:42 EST 2016
null\:merge=bfe76fb3f3c34d68b873d0acf715e2145e4cb805
HEAD=bfe76fb3f3c34d68b873d0acf715e2145e4cb805

Started by upstream project "jbosstools-build-sites.aggregate.child-sites__pull-request_master" build number 1
originally caused by:
 GitHub pull request #221 of commit 50c10ad83d250d2b86f5697c4581ba8f9cb4937d, no merge conflicts.
...
Fetching upstream changes from git://github.com/jbosstools/jbosstools-build-sites.git
 > git -c core.askpass=true fetch --tags --progress git://github.com/jbosstools/jbosstools-build-sites.git +refs/heads/*:refs/remotes/origin/* +refs/pull/*:refs/remotes/origin/pr/*
Checking out Revision bfe76fb3f3c34d68b873d0acf715e2145e4cb805 (refs/remotes/origin/pr/221/merge)
 > git config core.sparsecheckout # timeout=10
 > git checkout -f bfe76fb3f3c34d68b873d0acf715e2145e4cb805

-DghprbActualCommit=50c10ad83d250d2b86f5697c4581ba8f9cb4937d
-DghprbPullId=221
-Dsha1=origin/pr/221/merge
"-DghprbPullDescription=GitHub pull request #221 of commit 50c10ad83d250d2b86f5697c4581ba8f9cb4937d, no merge conflicts." 
-DghprbActualCommit=50c10ad83d250d2b86f5697c4581ba8f9cb4937d