Added parsing of mesh points in binary format

[filippo-biondi]

No description provided.

[ndem0]

Dear @filippo-biondi, can you also add a small test to check the behaviour?

[filippo-biondi]

I extended the tests present in tests/test_openfoamhandler.py to check also the reading of the mesh in binary format.
As input for these tests, the mesh already present in tests/test_datasets/openfoam_mesh and tests/test_datasets/notime_openfoam_mesh have been converted into binary format.
The added tests cover the changes of both this pull request and #48