Add support for XSLT transformations

[jakelandis]

XML transformations that are complex or element/attribute names are unknown ahead of time may be difficult to do with existing tools.

XSLT can provide rich transformations on XML documents to help solve some of the more complex transformations.

Support should be added to offer XSL based transformations with a simple contract back to the event object. Perhaps the contract could be to bring all data to a pre-defined element, or perhaps move all desired event objects as single valued elements under the root node.