XSLT based scrapers

This is not really tested or ready yet but it's working on OSX. Would need some Windows & Linux love.

Simple really: support XSLT transforms in scrapers, so we can do XML->XML conversions  logic (foreach, if/select/etc). This works great for things like, e.g. MusicBrainz that already spit out XML documents to us. The key is that XSLT also works on HTML. So for processing HTML documents we can also do HTML->XML parsing much easier and have a lot more logic.

Want to get your thoughts and feedback on this one. What needs to be considered here, how can we test this, etc?

See the MusicBrainz example in the second commit. The XSLT transform means we no longer need the RegExp's to build the details structure. I haven't removed the RegExps. The way I've written this we can combine XSLT and RegExp to best effect and the XSLT engine should work straight into buffers like the current RegExp processing.