removed a lot obsolete code

src/amdis/linear_algebra/mtl/SystemMatrix.cpp

src/amdis/linear_algebra/mtl/SystemMatrix.hpp

src/amdis/linear_algebra/mtl/SystemVector.cpp

src/amdis/linear_algebra/mtl/SystemVector.hpp

src/amdis/linear_algebra/mtl/UmfpackRunner.hpp

src/amdis/utility/MultiIndex.hpp