Compiles with HEAD
Restructured folders to remove devel / archive
Reflected dir structure change in cabal file.
Smallish twiddles to main files; big reimplementation in ByHand.

This will lead to an *exponential* decrease in runtime size + speed.
And, of course, that means also an *exponential* decrease in compile
time. Why? Because there were two copies of singletons stored *at
every level in a tree*. Yuck!! Why didn't I (or my reviewers) notice
this before?? Now, using an unsafeCoerce trick learned from Edward
Kmett, I can cast a Sing to a SingI in one step, avoiding the need
for the explicit SingI's. Supposedly, a new feature in GHC (coming
Real Soon Now) will allow me to avoid using unsafeCoerce, because
what I'm doing is actually safe. See singInstance in ByHand.