Import MediaWikiBot PHP Class

Summary:
The infographics tool requires this class to query MediaWiki wikis
and so use them as a datasource.

Fixes T1575.

Author: Kaleb Heitzman <jkheitzman@gmail.com>
License: MIT

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1575

Differential Revision: https://devcentral.nasqueron.org/D2156