Major changes

OpenDeck is now considered stable or at least final beta.

Changes include:

*completely re-written HDD reading code and merged into OpenDeck library
*almost complete re-write of button reading code
*rewriten LED part of code
*minor layout fixes
*added final cable plate design
*PCB layout changed for Arduino Nano
*minor circuit changes
*added PCBs for mounting below buttons/leds/pots
*added MIDI library
*added parts list
*updated terms
*many small fixes