Merge branch 'feature/marker' into 'develop'

examples/init/marker.dat.2d

src/amdis/Marker.hpp

src/amdis/Marker.inc.hpp

src/amdis/ProblemStat.hpp

src/amdis/ProblemStat.inc.hpp

src/amdis/ProblemStatBase.hpp

src/amdis/StandardProblemIteration.cpp

test/CMakeLists.txt

test/MarkerTest.cpp