* Port DIRECT_PINS from split_common/matrix.c to matrix.c
* Reorder matrix.c to remove foward declaration and match split_common/matrix.c
* Refactor nano to use DIRECT_PINS
* Reorder matrix.c to remove foward declaration and match split_common/matrix.c
* Add DIRECT_PINS documentation
* Reorder matrix.c to remove foward declaration and match split_common/matrix.c - fix logic from inherited from split_common
* Add DIRECT_PINS documentation - review comments
Many instances in the QMK Docs referenced KEYMAP macros, which is outdated terminology.
Replaced most instances of KEYMAP with LAYOUT, to reflect the desired usage.