removed using namespace std from pdbwriter.h and added std to strings
removed using namespace std from pdbwriter.h and added std to strings

MrTheodor/csg,MrTheodor/csg,MrTheodor/csg,votca/csg,votca/csg,MrTheodor/csg,MrTheodor/csg,votca/csg,votca/csg