some more cleanup/simplification
Merge branch 'master' of http://users.dune-project.org/repositories/projects/dune-multiscale

Conflicts:
	dune/multiscale/fem/elliptic_fem_matrix_assembler.cc
hides getting subgrids out of the list, instead get gridparts

This allowed me to identify the very few instance where the _actual_
subgrid is used. All of which seem to be unnecessary.
grep for "//! MARK actual subgrid usage"