Minimal port of PrStoreUTHit to functional conditions derivation

minimal version of !1772 (closed)

As a side-product of moving to functional conditions derivation, also the base class has been changed from GaudiAlgorithm to Gaudi::Algorithm. This implies a few additional changes are required, eg. replace use of Warning with MsgCounterMSG::WARNING, and dropping the use of counter(...) in favor of using Gaudi::Accumulators::Counter.

Please note that the latter implies (as is) a bit of loss of information: no information is accumulated 'per sourceID'. If that is really required, one has to know a-priori the range of (possible) sourceID and either create a vector of counters, or introduce a histogram based on Gaudi::Accumulators (which is not yet available)