Make -a --allow a repeated option?

For consistency with other repeated options, rather than comma-separated list which is something we (should) only use for compiled-in default values. So, will not change how folks do the compiled-in defaults, but if specifying allowed IPs manually on the command-line they would have to be -a val -a val rather than -a val,val.

EDIT: see comment below on the behavior we intend to fix for this -- both repeated option and the possibility to have a comma-separate list.