Add ReadTheDocs and tidy doxygen annotations #501

Job	Run time
macosx (11, xcode, 13, Debug, macos-11, shared64 static64)	1m 15s
macosx (11, xcode, 13, Release, macos-11, shared64 static64)	1m 13s
macosx (17, xcode, 13, Debug, macos-11, shared64 static64)	1m 16s
macosx (17, xcode, 13, Release, macos-11, shared64 static64)	1m 9s
macosx (11, xcode, 12, Debug, macos-11, shared64 static64)	1m 39s
macosx (11, xcode, 12, Release, macos-11, shared64 static64)	1m 13s
macosx (17, xcode, 12, Debug, macos-11, shared64 static64)	1m 11s
macosx (17, xcode, 12, Release, macos-11, shared64 static64)	1m 13s
macosx (11, xcode, 11, Debug, macos-11, shared64 static64)	1m 7s
macosx (11, xcode, 11, Release, macos-11, shared64 static64)	1m 12s
macosx (17, xcode, 11, Debug, macos-11, shared64 static64)	1m 12s
macosx (17, xcode, 11, Release, macos-11, shared64 static64)	1m 5s
	14m 45s

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