Add Jenkins bits to git

Currently, we have a ton of scripts in Jekins input manually, this
is a bit of a hassle since any changes need to be synced a few times.
I'm going to begin to strip the commonly used functions into shell
scripts stored in WMCore's git repository, so updating there will change
everything else simultaneously
Merge pull request #4546 from PerilousApricot/feature/move-jenkins-into-git

Add Jenkins bits to git