Remove accidentally duplicated model-specific peripheral driver files.

Add more include protection macros to give the user warnings when they try to manually include private driver header files, instead of the public driver headers.

Make board specific and device peripheral specific drivers' file documentation copy over to the module documentation, so that it is visible in the normal module view of the library documentation.

Added support for the Dataflash mounted on the XPLAIN board. Added new XPLAIN_REV1 board target for the first revision XPLAIN board, which used a different (smaller) Dataflash IC to later revisions.