Various fixes for RunJobs.php

* Use URL parameters for "wiki" parameter
* Work around bugs in the MediaWiki class accessors
* Enabled error logging so fatals show up
* Added a POST verb sanity check

Change-Id: I4b60c6d4f2f2b32a7afbbbd1e4c6e226fd2d92e1
Merge "Various fixes for RunJobs.php"