(captiveportal, new) change rc script to use cp instead of rsync (which is not installed by default) and change file ownership to chroot user

PR: https://forum.opnsense.org/index.php?topic=1730.0

Firmware update, proposed addition of missing translations

I know, gettext('2') et al looks stupid, but not having a complete
gettext() wrapping only leads to bugs later on...

See: Refused to set unsafe header "Content-length"