Add mw.ext.TitleBlacklist.test

Add lua method mw.ext.TitleBlacklist.test(action, title), which tests
whether a titleblacklist entry is active for a given title and action, and
if so, returns details of the entry.

Change-Id: I4360d1ad4e602d58dabd12b683d338a0e09a2950
Merge "Add mw.ext.TitleBlacklist.test"