Bug 1090689 - Add MPL2.0 headers to the repo

This work fixes part 4 of Bugzilla bug [1090689](https://bugzilla.mozilla.org/show_bug.cgi?id=1090689).

This adds missing MPL2.0 headers to files in the treeherder-node repo, in its new repo location under `/mozilla`. There were a couple of empty white space corrections and a bit of tidy up along the way.

Adding @maurodoglio for review.