Merge *optioninfo.h to *option.h.

Merge *optioninfo.h to *option.h.

Merge each *optioninfo.h header to the header that declared the
corresponding public option classes (setManagerForSelectionOptions() was
moved to selectionoptionmanager.*).  After 030c229 (I143592ed), there is
little need to have these in separate headers, as the OptionInfo classes
are now required when creating options.

Not having the implementation split over so many headers makes the code
easier to understand and to maintain, and this outweighs the small
benefits from being able to use the OptionInfo classes without adding a
dependency also on the Option classes (only OptionVisitor would
currently benefit from that).

Adjusted Doxygen documentation for OptionInfo and SelectionOptionInfo
(and some of the files) as part of the reorganization and did some
include cleanup related to the reorganization.  Otherwise, this change
only moves existing code around with no functional changes.

Change-Id: Ic1c62739beca09028887179da26b33516d01624b