Feature/cleanup of eigenvalue solver docs

improve structure of the doxygen documentation to make the eigenvalue solvers visible and hide implementation details

dune/istl/CMakeLists.txt

@@ -42,6 +42,7 @@ install(FILES
    solvertype.hh
    spqr.hh
    superlu.hh
+   superlufunctions.hh
    supermatrix.hh
    umfpack.hh
    vbvector.hh