import systematic enum from WH

improved implementation: now within namespace and struct (similar to
what 'enum class' will be in c++11)
add EventFlags::passAllEventCriteria
nonstatic weight components
add DileptonVariables
filter jets, fill vars
DileptonVariables : add mcoll*
DileptonVariables: split passLeptonPt
Selector : add split counters and increment them
yield Sherpa_CT10_lllnu_WZ