Enable uploads and InstantCommons by default

Because MediaWiki-Vagrant runs on a virtual instance that only you can access,
I see very little downside to enabling uploads and InstantCommons by default.

Change-Id: I7fb67f4315bd78f580d6e2ef0867019c76a290be
Add mediawiki::parsoid class

This change adds a mediawiki::parsoid class which configures a Parsoid HTTP
service on the Vagrant virtual machine.

Change-Id: Ib81213c91ecc9af5ddf5827d886e6a5f67d17f7e