Use when special form instead of if+begin combos.

(This did not exist in Microscheme originally.)

(Technically it still doesn't outside my one branch that hasn't gotten
merged at the time of this writing.)
Add EVEN MORE comments.

The code:comment ratio in menelaus.scm is now 1:1.
Add a ton of comments.
Fix a bug with releasing key zero not always working.
Now member is part of microscheme.
Add license; clarify reset problems.
Fixed that bug.
Haha oops; no negative numbers in microscheme.
Fix a bug in releasing fn-layer shifted keys.
Don't crash when seven keys are pressed.
Microscheme's apply is pretty janky.
Implement press/release tracking.

This fixes the layer-switching bug which has been so problematic on
this firmware and on atreus-firmware.
Refactor to use lists for scans of the matrix instead of vectors.
Better layer support; disable L2 for now.

Need press/release tracking before sticky layers will work.
Finish multidvorak layout.
A few layout mistakes.
Support fn layer and arbitrary functions in layouts.

There is still a bug when you release the fn key but still have
another key held down, along with a failing test case.