Some suggested graphics

 1) RG thinks it would be of some use to have a plot function that
  takes a flowFrame as input and produces a lattice view where Time
  is on the x-axis in all, and the other fields are on the y-axis.
  Each plot should have a smooth of some sort - and potentially
  some other visualization tool to help find anomalies wrt time.


 2) unified treatment of filters and gates -DS

 3) parallel coord plots for flowSets -DS
