Basic support and mapping stats for the Wikimedia Commons

I've added support for the Commons by adding a list of Commons namespaces containing metadata (Main, File, Category, Template, Creator, Institution) and modifying the ConfigLoader to ensure that these pages are processed. I then modified the LabelExtractor to use these namespaces as a test, and the InfoboxExtractor and RedirectExtractor so that I could run the stats extraction, whose results from the Commons dump of 2014-05-08 is included in this pull request.

This is my very first pull request on DBpedia as a Google Summer of Code student, so please feel free to correct anything or make any suggestions that would improve my code!