Improve vtkParticleTracerBase filters

The ParticleTracer/ParticlePath/StreakLine filters which are subclasses of vtkParticleTracerBase have the following improvements:

1. Multithreaded using vtkSMPTools. Multithreading is used when there is only one MPI process, and the number of particles is greater than 100.
2. Now have InterpolatorType which can either use a cell locator (default) or a point locator for interpolation.
3. Instead of the StaticMesh flag, it now has the MeshOverTime flag which has the following values:
   1. Different: The mesh is different over time.
   2. Static: The mesh is the same over time.
   3. Linear Transformation: The mesh is different over time, but it is a linear transformation of the first time-step's mesh.
      1. For cell locators, this flag internally makes use of the new vtkLinearTransformCellLocator. This way the locator is only built once in the first time-step.
      2. For point locators, this flag internally re-uses the same cell links, but rebuilds the point locator since there is no vtkLinearTransformPointLocator yet.
   4. Same Topology: The mesh is different over time, but it preserves the same topology (same number of points/cells, same connectivity).
      1. For cell locators, this is equivalent to MeshOverTime == Different.
      2. For point locators, this flag internally re-uses the same cell links.