[WIP] cekees/wip parallelize multigrid

Continuing work  on the parallel projection/restriction operators  here. Several issues need to be addressed

- how/when to pull in global mesh for multiple  levels
- whether to bite the bullet and implement compact hierarchical meshes
- work out the best way to build the row and column spaces l2g mappings and call petsc4py 
- whether  or not to go ahead and support trace operators and projections between non-matching domains