Compute mesh intersection between surface and boundary of volume

[justinlaughlin]

When a subsurface is a superset of the boundary of a subvolume, we need to use the "nan" (max size_t) values in cell_map to restrict the mesh.

[justinlaughlin]

Commit d226aec attempted to use the nan values of cell_map in intersection_map and dx_map. Forms can be assembled but once a differentiation occurs dolfin refers back to the original cell_map. Solution needs to involve creating new MeshViews using the calculated intersections