SubDomain::apply_markers() could mark also entities with at least one vertex inside

This is rather a deficiency in method than a bug.

Consider that method could take an optional bool argument which would ensure that entity is marked if at least midpoint is inside and/or another optional bool argument ensuring marking of entity if at least one vertex of set (incident vertices + midpoint) are inside.

This could resolve naturally an issue while marking CellFunction by two or more disjoint Domains covering whole mesh but not matching with facets. In this case there exists cells which are not entirely in any Domain and are not marked.