Add Fn to Command_L

It would be nice to have a mapping from Fn to Command for all letters/numbers/symbols but NOT FN keys or Tab/Escape/Space.  This makes it easy to use a MacBook Cut/Copy/Paste like a PC without messing up the Function keys like Brightness, Volume, etc.
Merge pull request #197 from Identifier/patch-1

Add Fn to Command_L *except* Function keys