Add adaptive interparcel mixing

The filamentLimit is adapted to the disorder degree of parcels, so the
mixing occurance depends on the flow deformation.
Replace TracerMeshCell with MeshAdaptor

To use the IOManager in GEOMTK, the too object oriented TracerMeshCell is
replaced by MeshAdaptor. In MeshAdaptor, the tracer density and mass are
organized into ScalarField which can be inputted or outputted by IOManager
directly. Now the meshed tracer density and mass in AdvectionManager are
outputted by AdvectionTestCase.