Adding support for query string params to mw.util.wikiGetlink

This will enable us to easily migrate MobileFrontend from
using M.pageApi.getPageUrl (mobile custom version) to
mw.util.wikiGetlink.

Includes a unit test.

Change-Id: I5224a0910a822f1c3b1b34f505dbcdf879052b39
Merge "Adding support for query string params to mw.util.wikiGetlink"