added DOFVector test

src/amdis/linear_algebra/Common.hpp

src/amdis/linear_algebra/DOFMatrixBase.hpp

src/amdis/linear_algebra/RunnerInterface.hpp

src/amdis/linear_algebra/istl/DOFMatrix.hpp

src/amdis/linear_algebra/istl/DOFVector.hpp

src/amdis/linear_algebra/mtl/DOFMatrix.hpp

src/amdis/linear_algebra/mtl/DOFVector.hpp

src/amdis/linear_algebra/mtl/KrylovRunner.hpp

test/CMakeLists.txt

test/DOFVectorTest.cpp