[rahqenfa] Permuting a keyboard layout

Create keyboard layout which can be learned gradually as modifications to QWERTY: a series of small changes which can be learned over time.  Swaps of 2 keys are the smallest type of change, then cyclic 3-permutations.

Avoid any key from participating in multiple (successive) permutations.  Only a subset of permutations of the original layout are reachable.