Create object to represent OpenFOAM case

[petebachant]

Some members:

• app_call_sequence
• controldict (a FoamDictionary object)
• blockmesh_dict
• domain_dimensions
• trimesh_files
• function_objects (come from controldict.functions)

There can also be derived case types, e.g., ExternalFlowCase.

Example usage

case = foampy.Case()
case.dicts.blockmesh["convertToMeters"] = 0.001
case.app_call_sequence = ["blockMesh", "pimpleFoam"]
case.run(nproc=4)
case.post_process()
print(case.post_processing["forces"]["0"].fx.mean())
print(case.summary()) # Pandas series
case.clean()

[petebachant]

Will probably depend on #26.