Updated mediawiki/extensions
Project: mediawiki/extensions/Model  2e2ddf034955d2351ccddee6331386f36d0da1bf

Consistency tweaks in preparation for adding extension to translatewiki.net

* Extension description key to code convention
* Add message documentation
* Add URL

Change-Id: Id6961c00151782cef8b9e189ca6e282006662f44