ac1512

Results 2 issues of ac1512

[Draft: dont merge] Changes to close_mesh.F90 and gflag_constr_parents.F90: without these changes, anisotropic adaptivity fails under certain configurations as it results in two levels of irregular vertices.

application
WIP

Features added to allow adaptation for linear hex elements and src/meshmod/refine.F90 and closemesh.F90 to allow double- constrained vertices.