Performance tweaks

[edding3000]

what

Range based for loops with references are already used in this project, but in a few places not. I am not sure why. I changed this code locations and executed unit tests. Also use '*' for pointers when using auto keyword, makes it more readable.

why

Improve performance a little bit.

questions

"const auto&" could also be used in many places. Is there a reason why it is not used?