Support for KMAC

Hi tmk

Here's a new pull request for you.
I don't know if you are interested in it though.
I put it here and let you decide.

This pull request implements support for the KMAC.

I have done the following things.
* Implemented general support for controlling backlighting.
 * The backlight state is stored in eeprom.
 * Defined actions to control backlight level and toggling it on and off.
* Implemented a project that supports the KMAC PCB and uses the new backlight functionality.

I don't know if I have done things the way you want.
Please let me know if you want something done a different way.