reimplement interpolate function with averaging

src/amdis/CMakeLists.txt

src/amdis/common/FieldMatVec.hpp

src/amdis/common/FieldMatVec.inc.hpp

src/amdis/functions/CMakeLists.txt

src/amdis/functions/HierarchicNodeToRangeMap.hpp

src/amdis/functions/Interpolate.hpp

src/amdis/gridfunctions/DOFVectorView.hpp