[ellipticMsFEM] removed superfluous include
[traits] Use cmake-defined grid type
[msfemSovler] use msfem projection instead of heterogenous

Heterogeneous projection was not working in our
setting as values on coarse cell boundaries were
set to one of the values in question instead of
computing the mean value.
bugfix: space must not be constructed in local scope

Constructing the space in the local scope gives
undefined behavior later on when fem_solution is
used.