replaced PATH with PATHS and ALUGRID_DIR with ALUGRID_ROOT in FindALUGrid.cmake
Merge branch 'repair_FindALUGrid_cmake'
new strategy to find alu grid
cleanup of FindALUGrid
search also in system path for alugrid
Merge branch 'master' into repair_FindALUGrid_cmake
[FindALUGrid.cmake] Add comments, reformat code.
[FindALUGrid.cmake] Make ALUGrid check work again.
Fix typo and reformatting in dune/grid/test/CMakeLists.txt.
[FindALUGrid.cmake] Improve CMake check for ALUGrid.