It's finally time to make the theory and implementation pages consistent in their use of cube coordinates. The theory page had used an x,z,y cube coordinate system and the implementation page used q,r,s. This is part (a) but part (b) was in 2022 Feb.

- [x] Change x,z,y to q,r,s
- [x] Emphasize that axial and cube are essentially the same, but axial calculates s when needed and cube stores s preemptively.
- [x] Change sections of the page that treat axial/cube separately to treat them as one system.
- [x] Link the axial and cube introductory diagrams together
- [x] Define cube_add, cube_subtract, cube_scale helper functions
- [x] Describe axial version of line drawing
- [x] Point to axial_round from Jacob Rus
- [x] Change variable names from math-like ("P") to code-like ("point")
- [x] Change variable names from coordinate system specific ("cube") to generic ("hex")
- [x] Make a copy of v1, v2 of this page publicly accessible