tracking HLT validaiton

this pull request is meant for updating the list of plots used by the tracking HLT validation
1. add also hltIter4Merged monitoring
2. add efficiency and fakerate for 
    hltPixelTracks, 
    hltPFlowTrackSelectionHighPurity, 
    hltIter1PFlowTrackSelectionHighPurity, 
    hltIter2PFlowTrackSelectionHighPurity, 
    hltIter3PFlowTrackSelectionHighPurity
    hltIter4Merged

this pull request needs the update from Martin on the HLT output content (there was a typo in a collection)