LED driver properties now can re-define an array
for their individual mapping from key offsets to LED indices.
This array is both constexpr (can be used at compiletime) and
stored in PROGMEM. The latter is used by the LED driver base
class to map key offsets to LED ids at runtime.
Signed-off-by: Florian Fleissner <florian.fleissner@inpartik.de>