[bugfix] use correct CMake variable to check whether dune-corepy was found

See merge request !7

[bugfix] add missing header to make headercheck pass

See merge request !6

[bugfix] make nightly builds compile after changes in subIndex interface.

The recent change subIndex in the dune-grid interface seems to cause a problem in dune-fem. 
@martin.nolte: Please take a look. The suggested change at least make the code compile.

See merge request !5

remove genericgeometry subdirectory from dune-geometry

The removal of the genericgeometry subdirectory in dune-geometry will require some minor changes to dune-spgrid. This merge request collects those and should be merged once the corresponding branch in dune-geometry is merged, too.

See merge request !4

[bugfix] fix count flops grid type.

This make the GRIDTYPE for SPGrid with the coordinate type being Dune::Fem::Double work. The previous version did not work.

See merge request !3

[bugfix] add missing header file



See merge request !2

use std::{remove_const, conditional} instead of the Dune version



See merge request !1