Merged requested to merge sponce_SinkRefactoring into master
this includes 2 main steps :
- Extracted a BaseSink class from current implementation to make other sinks simpler and allows every sink to benefit from regexp based selection of entities
- register all histograms of the HistogramSvc to the default RoothistogramSink
Thus the next question is : can we drop the HistogramPersistencySvc ? Answer is actually no for the moment, as it's used also by the NTuples
Requires lhcb/Rec!3261 (merged) in order to not break lhcb code.