Replace 'permutations' with 'positions'

We were using permutations to mean both the total number of positions and
the permutation (location) of the pieces. This changes the text so that
positions = permutations * orientations.
Every *three dimensional* cube has eight corners
Merge pull request #2 from chrishunt/pochmann-updates

Update 'How Many Positions on a Rubik's Cube'