Trigger-emulating preselection has been implemented

The preselection is required by triggering MVA electron ID. ECAL-driven isolation exploited in the preselection is corrected for the known problems [1]. However, the corrected isolation is very often negative, and it must be investigated.
[1] https://twiki.cern.ch/twiki/bin/view/CMS/EcalIsolationCorrection2012Data
Debug output removed

Matteo Sani (EGamma HLT convener) has confirmed privately that the negative values of isolation after the correction are expectable.
Merge branch 'trigger-emulating-preselection'. This fixes #9

The branch implements emulation of trigger preselection required by MVA electron ID.