Open compiler warnings

This is a list of warnings in dune-grid emitted by compilers on the current master after the release 2.10. Maybe we can fix a few of these

• dune/alugrid/common/bisectioncompatibility.hh:120:18: warning: variable bndFaces set but not used
• dune/alugrid/common/bisectioncompatibility.hh:1094:9: warning: variable sizeOfV1 set but not used
• dune/alugrid/common/bisectioncompatibility.hh:1095:9: warning: variable sizeOfV0 set but not used
• dune/alugrid/3d/grid_imp.cc:54:9: warning: variable count set but not used
• dune/alugrid/test/test-dgf.cc:25:13: warning: unused variable rank
• dune/alugrid/test/checkintersectionit.hh:6:2: warning: "Using overloaded checkintersectionit.hh because of manifold normal checks not being fully discussed yet! See MR !320 in dune-grid!"
• dune/alugrid/test/test-alugrid.cc:115:15: warning: unused variable 'id'