add information to VPTrackMonitor to study residuals

• replace getResidual function by node.residual()
• add additional track information to node and track tuples
  • add flag if residual is x- or y-residual
  • add flag if track is only hitting left or right VELO half or if it is overlap track (based on code copied from @anbeck )
• add histograms of mean residuals as function of track slope

cc @anbeck @bpagare @rmohamme