Added convenience static constructor.
Added comment.
Changed subcell/dof entity ownership policy to prefer larger entities (i.e. in isotropically refined meshes, the owning entity will be the constraining entity).
Added assertion against attempts to h-refine inactive cells.
Fixed error in call to 2D mesh constructor.
Various tests and bug fixes for GMGTests.
Various tweaks (including new CLI options) to StokesCavityFlowDriver3D.