Added manifold, copying over the old concept, but retaining dim. Made Boundary<dim...

Added manifold, copying over the old concept, but retaining dim. Made Boundary<dim,spacedim> derived from Manifold<dim,spacedim>.

Added specific instantiations for invalid accessors. Moved get_default_quadrature into an anonymous namespace.

Made Boundary derived from FlatManifold, and made sure that nothing broke. Added get_new_point_on_cell/hex. Made get_new_point_on_quad not throw an exception in 2d.

Created Manifolds namespace, and made specialization of get_new_point_on_hex only in 3d, instead of multiple specializations for when dim not equal 3.

Added test flat_manifold_01

Fixed 2d problems.

Fixed 3d. Now all tests work, except from machine precision errors.

Added a new test for flat manifold checks on faces.

Completed documentation of manifold and tria_boundary.

Removed commented out functions from Boundary<dim,spacedim>, whose default has been moved to Manifold<dim,spacedim>

Fixed periodicity of FlatManifold, and added a test for it.

Fixed comment on periodicity.

Removed commented instantiations.