Parse pages and text in context of user language

and text in context of the current page the user is on, instead of "API".

This allows template-based i18n, until on-wiki i18n is fully supported
(e.g. with Gadgets 2.0) as well as using constructions that are
title-dependent like "[[{{TALKPAGENAME}}]]" to work.

Bug: 55664
Change-Id: I8f75c99a41674030881961e958d32cbe8c6bf4de
Merge "Parse pages and text in context of user language"