Removed superfluous argument in BuildNewModel() in itkPartiallyFixedModelBuilder
Added a representer for vtkUnstructuredGrids.
Added python wrapping for this representer.
Actually added the Representer files.
added missing wrapping file.
Removed an unneeded assert.

The assert referred to a member variable, that was removed in one
of the earlier changes. It thus led to a compilation error, when compiling
in debug mode.
bugfix: domain was not set properly when representer was loaded
bugfix: changed test to return false when it fails