Plot particle trajectories through time

[pbosler]

With output to paraview via vtk data files, we can make animations of the solution fields. In an animation, particle motion is easier to perceive but in a printed figure, it's very difficult. We need to be able to plot trajectories over time to make particle motion in printed figures more apparent. This either requires custom programmable filters for paraview (which only plots one time step at a time) or a custom vtk program.