You can't have two mainpage items, and the second was just being
ignored. This restores them, which makes the left side list longer,
which we may or may not like, but it's at least how it was documented to
be.
* Include the doc-swm050.h core file that defines the base groups.
* Fix/tweak groupings to make things consistent with other targets.
* Drop redundant type information. That's all included from the function
signatures automatically by doxygen.
* Added register descriptions from datasheet.