[cleanup] Use range for instead of std::for_each

This commit replaces all use cases of std::for_each(..., std::mem_fn(...)) by a much more readble plain range for. It does not replace other uses, where this may be more controversial.

This is a follow up to !115 (merged).

Locally, the poweriterationsuperlutest fails for this branch, but this is also true for the master.

assigned to @smuething

mentioned in commit 798df797

merged