More massive refactoring.  System still is in a bad state; it does not
run or even compile.  A lot of work to do.
The library remains broken.  The fully-applied type of an operator must
be rewritten when it is used in an apply to yield an OpApply.  A
decision must be made about whether context is actually needed during
matching and rewriting, or if builder will suffice.  In short, a lot of
work remains.
Significant improvements, but lots more to do.  System is still broken,
but the basic structure of dependencies is pretty well established.