Add Treeherder to js/py programming language categories (1046596)

This fixes part 1 of Bugzilla bug [1046596](https://bugzilla.mozilla.org/show_bug.cgi?id=1046596).

This adds the suitable Treeherder content to both js/py categories. @jdm please check to make sure the py granularity level (ie. a sibling to items like "Release Enginnering" and "Firefox") makes sense to you. I've only updated en.ini based on the older checkins to the repo where new items were similarly added. I assume the other locales get suitably generated.

Let me know if I've missed something. I've iterated with @jeads on the wording and he's happy with it.

Tested on Windows:
FF Release **31.0**
Chrome Latest Release **36.0.1985.125 m**
Adding @jeads for comment since he and I wordsmithed this together. Treeherder comprises all the items we listed, as it is not just the dashboard UI. We also wanted to engage people who might be interested in data model or web services, and might not otherwise know.