Add jenkins-job-builder as a broken out project

There is a wholly separate dev community around jenkins-job-builder
that it would be nice to track. Leaving jjb also in infra though,
because it's interesting to track there as well.

Change-Id: I61f29f78bb6300f9b0c9fe9522172f090234f0b9
Merge "Add jenkins-job-builder as a broken out project"