Initial add of the generic optimizer code

Before digging into this code, look at the Rules implemented at the bottom of DagOptimizer.

There are several TODOS here:

- [x] After I split the code into separate files, I started hitting a scala 2.9 compiler bug, that I don't hit in 2.10. I'll try to work around, or possibly hope that Twitter finally gets on 2.9 before we need this.

- [x] Tests tests tests. I played around at the repl, but clearly we need super hardcore tests for any optimization framework.

- [ ] Actually call this code from an existing platform.
I am still going through this review, and kind of just started, but why do we need T[A, B[_]] if A fixes B? We're ensuring that N is a more general container, but that in this case, it is fixed on A? I guess the goal is to be able to keep N, but move around transformations on types? Like I said, still making my way through, just hoping you could talk to that a little bit.