Updated iterators
Updated iterators

* Use const auto & instead of auto &&
* Use const auto & instead of for(size_t pos = 0; pos < ....)


Former-commit-id: fefa43a593ab6c36d12ce1324698716e0faf92a4
DavidAce/DMRG,DavidAce/DMRG,DavidAce/DMRG,DavidAce/DMRG