The previous two options were COL2ROW, ROW2COL; this adds CUSTOM_MATRIX
to disable the built-in matrix scanning code.
Most notably, this obviates the need to set MATRIX_ROW_PINS or
MATRIX_COL_PINS.
Fixed compiler warning by including bootloader.h in keymap_common.c.
Changed FORCE_NKRO to only be applied if NKRO_ENABLE is defined.
Added extra documentation to the template config.h