Pro Micro vitamin

Added board for Pro Micro and Pro Mini - main difference is micro USB connector instead of 6 min serial connector.

Have made board size configurable, though the variables as defined are the only board size being used - regardless, amount of header pin holes will grow according to size (despite this not really being useful right now! ;)

As for board components, I have just blocked out an area for the USB connector, and another (transparent) area for board clearance (which can be disabled).