Board specific HW configuration is now collected in a single .c
file for each board. This HW configuration is #include'd into
the FW, BL and BU builds for each board.
These new .c files are found in:
flight/board_hw_defs/<board_name>/board_hw_defs.c
Parts of this information were previously duplicated between
the BL and FW builds. This commit cleans up the duplication.
Using a #include on a .c file is a bit ugly but it allows us
to ensure that all of the symbols in the board_hw_defs.c file
are *ONLY* used in the PIOS_Board_Init() function for each
software build.
