Core selftype constraints defined.

I've added the definitions of the constraints now.

My projected timeline for this weekend through the next:

This weekend: finish writing the sections I've read so far.
Saturday - kill off boolean encodings, start the next reduction.
Sunday - finish reduction from SAT to CS constraints.

Next week: read up on the next reduction, fill it in.

Next weekend: start reading up on next paper (recursive subtyping).

Comments welcome as always.

--Carl