SusyPlotter::Process: increment readin, call selectObjects with explicit opts
passSrSs: dilepton type not taken as input, but computed
do not fill PR_NONE histos (useless), delay weight calculation
define activeDatasets
fix: use datasets rather than datasets names
define WeightComponents and add it as a new member
SusySelection::increment: now pass the weight components as inputs
drop obsolete getPythiaBbCcScaleFactor (not running on these samples)
getBTagWeight: pass jet collection as argument
replace getEvtWeight with cacheStatic* + computeNonStatic*

Details:

getEvtWeight was a mix of factors that depend only on the event, and
factors that depend on the selected objects.  It is now split in two
parts:
+ cacheStaticWeightComponents
+ computeNonStaticWeightComponents
In particular, the cacheStaticWeightComponents will cache the value
coming from SusyNtAna::getEventWeight, whose call seems to be fairly
expensive (map lookup? we might want to cache it upstream...).