Add ReadTheDocs and tidy doxygen annotations #512

Job	Run time
macosx (11, xcode, 13, Debug, macos-11, shared64 static64)	8m 55s
macosx (11, xcode, 13, Release, macos-11, shared64 static64)	10m 18s
macosx (17, xcode, 13, Debug, macos-11, shared64 static64)	7m 35s
macosx (17, xcode, 13, Release, macos-11, shared64 static64)	11m 4s
macosx (11, xcode, 12, Debug, macos-11, shared64 static64)	10m 6s
macosx (11, xcode, 12, Release, macos-11, shared64 static64)	10m 52s
macosx (17, xcode, 12, Debug, macos-11, shared64 static64)	10m 4s
macosx (17, xcode, 12, Release, macos-11, shared64 static64)	10m 56s
macosx (11, xcode, 11, Debug, macos-11, shared64 static64)	12m 54s
macosx (11, xcode, 11, Release, macos-11, shared64 static64)	17m 48s
macosx (17, xcode, 11, Debug, macos-11, shared64 static64)	12m 58s
macosx (17, xcode, 11, Release, macos-11, shared64 static64)	18m 14s
	2h 21m 44s

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