Bugfix in utility function.
Added a set_labels function that set the label of tetrahedra inside a geometry.
Added a geometry that can contain several geometries. Also added an inverse cube (a point is inside if it is outside or on the border of the cube).
Using a MultipleGeometry as the design domain which means it is possible to combine geometries to create more advanced design domains.
Any geometry can now be inverted (is_inside function returns true when the point is outside the geometry)
Added a function that projects a point onto the surface of a geometry.