BAC-688 Restrict use of mcache query string parameter.

https://github.com/Wikia/config/pull/184 needs to be merged first.

The diff sans-whitespace looks better: https://github.com/Wikia/app/pull/1326/files?w=1

https://wikia-inc.atlassian.net/browse/BAC-688

@Wikia/platform-team