Added physical layouts for the following variants of numpads:
- With and without extra top row
- 2U plus key or 1U plus and backspace keys
- 2U 0 key or 1U 0 and 00 keys
- Full 1U grid/macropad layout
Other layouts exist, such as "southpaw" horizontally mirrored layouts,
and layouts with a fifth column, but those seem to be much less common.
Joel Spadin