Merge branch 'sponce_cleanup' into 'master'

Various cleanups, essentially around MonCounter/Rate

See merge request !425 (merged)

(cherry picked from commit a0affda2)

ec01d761 Cleanup step 1 : simplify MonCounter constructor 0e62c4dc Cleanup step 2 : make SerializeData a member function cd6b2b99 Cleanup Step 3 : drop useless Create_OutputService function fa3b7f7c Cleanup Step 4 : drop useless MAKERate function 1a74db7b Cleanup Step 5 : drop useless ClearLastCount function 618c3d60 Cleanup Step 6 : Simplify MonRate class 2257d55d Cleanup Step 7 : basic cleanup of CounterSubSys code 6158a4b1 Factorize non templated code of MonCounter into a baseclass 28b723d8 Proper template specializatin of MonCounter for atomic types fbf30780 Proper template specialization of MonCounter for pairs 0b811082 Proper template specialization of MonCounter for arrays 1ca24540 Proper template specialization of MonCounter for accumulators c7334d62 Proper template definition of MonCounter 91e354fd Factorize non templated code of MonRate into a baseclass 9e1a3bf8 Proper template specializations of MonRate for atomic/pair/accumulators acabbfb2 Dropped MonRateA, replaced by proper specialization of MonRate for arrays 919ad5a4 Moved declarations of template specialization of MonCounter/Rate to dedicated files 8b6aa50d Fixed some dependencies in cmake Credits to @clemencic 0a1df3a5 Dropped useless ADDEntry functions, and (now empty) handle files