Add USB descriptors for devices programmed through the Arduino environment

It looks like Arduino uses USBCore to assign vendor/board names to user programs that use LUFA. Here's a patch that (hopefully) adds the correct ones for the SparkFun devices covered in this board file.

There seemed to be a mismatch between the USB PID numbers in the boards.txt and bootloader definitions, though. I changed them all to be similar to the bootloader ones, but am not sure if that was the correct choice.

Thanks for providing your board support package! I based ours directly on it:
https://github.com/blinkiverse/Blinkiverse32u4_boards