Expect j and k to behave consistently in different modes

So, at least I expect `j` and `k` to behave consistently in normal, visual, operator and select mode and thus I'd use `noremap` instead of `nnoremap` for `j` and `k`. Was there some reason `nnoremap` was chosen over `noremap`? `noremap` does not affect the insert mode, if you're afraid of that, see `:help map-overview`.