MeasurementTracker redesign

MeasurementTracker Redesign, as presented in the RECO meeting on 2013-1019
Rebased to today's IB, and squashed to a single commit.
https://indico.cern.ch/getFile.py/access?contribId=8&sessionId=0&resId=1&materialId=slides&confId=265609
Note: HLT changes are needed, and HLT people are aware of it.