Merge pull request #95 from mhanus/fixes

is_const = false in default HermesXDFunction constructor
Some const updates.
Start with shared_ptr - for Mesh.
Add shared_ptr to Space.
Work on shared_ptrs.
Add SpaceSharedPtr for gcc.
Revert a change in Adapt::Adapt due to Agros.
Fixes in shared_ptr.
Progress on shared_ptrs.
Shared_ptrs work on majority of examples.
shared_ptr work.
A gcc fix.
Add some methods to Global.
Fix memory leaks.
Fixes in DG.
Clean up DG and forms.
Make parallel regions "almost" MPI compatible.
Assign DOFs sequentially in all spaces in every assembling step.
A fix.
Fix MeshView.