Monitor algorithm for event variables

Add algorithm which can histogram a single functor.

Needed for Moore!2798 (merged)

Phys/SelAlgorithms/src/VoidMonitor.cpp

@@ -11,8 +11,6 @@
 #include "Functors/with_functors.h"
 #include "Functors/with_output_tree.h"
 #include "Gaudi/Accumulators/Histogram.h"
-// #include "GaudiAlg/FilterPredicate.h"
-// #include "LHCbAlgs/Producer.h"
 #include "LHCbAlgs/Consumer.h"
 
 namespace {