Fixed: Doxygen configuration

The Doxygen configuration file caused warnings to appear about obsolete tags. (The version of doxygen that the file was created for was 1.7.1, which was released in 2010.)

This commit uses the automatic doxygen updater (doxygen -u) to update it to a more recent version (1.8.7).

Additionally, this commit changes the .doxygen file to build a docset by default. The effect of this is to simply emit a `Makefile` in the output directory that can be further used to compile a docset. Parameters for the project publisher and name were added for this docset.