wip adding traversal engine.
[broken build] see commit notes

I've been extending the CompareAdam.scala classes to separate out the "traversal" code.

Right now, the general outline is there, for generators and filters.  To get this to compile,
we'll need to update CompareAdamSuite in the tests at a minimum, and I'm not sure how to do this
quite yet.

Let's talk about this this morning?