Adding pixel hit monitoring histograms
this MR contains:
- requested renaming of the pixel monitoring tools to algorithms (Mon->Alg), e.g. here https://its.cern.ch/jira/browse/ATLASDQ-744
- PixelAthHitMonAlg skeleton now filled with monitoring histograms
- improvements of the filling of pp0 histograms and other smaller tunings and cleanup of the existing code.