Test IO codepath for mesh entities ordering

[Jan Blechta]

The tests have been added by acd3999 to test whether DOLFIN is in compliance with UFC ordering. This for now includes only internal mesh generation. To make all relevant codepaths tested some meshes loaded using IO should be put here. Possibly all the meshes enumerated there could also be tested by writing and reading back by writing some simple wrapper.

Preliminary assigning to Michal.