Counters: Improve doxygen
Assign the doxygen at the top of Countesr.h to the namespace so it
appears properly on the doxygen web pages. Also add a link to each
counter class to this detailed documentation.
cc @sponce
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Assign the doxygen at the top of Countesr.h to the namespace so it
appears properly on the doxygen web pages. Also add a link to each
counter class to this detailed documentation.
cc @sponce