Replacing mappings with XSL transformations

I'm not quite done with this yet, but it's an important change on the data integration side of things. We stretched our `RecordFormatMapping` concept to the max and it sort of broke (became way too complicated for my liking). So...I introduce to you [XSLT](http://en.wikipedia.org/wiki/XSLT)!

The idea is to store the transformations in files (right now in `lib/data/formats`) and transform each XML file being added into something that's easily readable by our `integrate_record_from_xml` method. Check out the one included in this PR.