Bug 50959: Pull the JSON schema from the Meta page.

This allows the schema to be pulled from a remote wiki. It also
allows the user to set three new configuration variables: the
title of the schema page, the API URL for the wiki, and the DB
name for the wiki.

Bug: 50959
Change-Id: Ia9a9447ee61d3fe254128ea392eb1a7168c763d7
Merge "Bug 50959: Pull the JSON schema from the Meta page."