[ufrsksjo] Rotations in many dimensions

Create a library for computing 90 degree rotations in an arbitrary number of dimensions.  We focus on 90-degree rotations (first) because those can be done by simple addition, subtraction, and permutation of coordinates.

And reflections.  4 dimensions (and more) have double rotations and so forth.

The tricky part will be defining an API that a human can understand, despite rotations in high dimensions being not intuitive.

Motivation was implementation of higher dimensional cubical twisty puzzles (replicating what has already been done by others).