Defines for electronics boards

Added boards.h which contains defines for all the board numbers, plus
some shorthand macros for less typing.
Clean up configs
Defines for electronics boards

Added boards.h which contains defines for all the board numbers, plus
some shorthand macros for less typing.
Clean up configs
Merge branch 'board_defines' of https://github.com/thinkyhead/Marlin into board_defines
Happy configs
Merge pull request #1195 from thinkyhead/board_defines

Defines for electronics boards