Bug 51273: Support per-wiki API proxies

We had to disable direct access to the API cluster in production as that was
breaking private wikis and wikis not hosted on the same cluster (wikitech).

This patch adds the ability to configure API proxy settings per wiki. This
lets us disable proxying for those wikis. We could also proxy them through
another service.

Change-Id: I042b8b091652374696c76aafe3964eca80dfc662
Converted jobs to use BacklinkJobUtils

* This greatly reduced the uselessly high number of jobs in the queue

Change-Id: I5d5af179c342c7246055a114718eed29abc07ee0
Merge "Bug 51273: Support per-wiki API proxies"
Improve parser test for bug 52760 (close tags are being stripped).

Split out the test for bug 52760 from the test for bug 17663, which should
make it more clear what's going on.

Change-Id: Iec7133e919a4ef35b781c92197009d889a659fd9
Merge "Improve parser test for bug 52760 (close tags are being stripped)."
Merge old repo

Conflicts:
	php/ParsoidCacheUpdateJob.php

Change-Id: Idb19449741fe17ba45c40c8f370fec4b9cc85c2a