Create LICENSE

Adding a license; wouldn't want people to hold me responsible for their machines getting hurt.
"optimizing" circle profile cuts

Instead of going to a safety height followed by a rapid move, to a
direct linear move to the center and up a z-step. From there the plunge
will only need to move down 2 z-steps (instead of the current
increasing number).
new demo program; all cuts, less space, verifiable.