Yes, "all done" means "completely done." In my experience, this is a very colloquial expression that is mostly used by and around children. i.e. after a child "goes potty" (goes to the bathroom), he or she might say "all done!," or the parent might ask, "all done?" It can also be used jokingly between lovers or close friends, i.e. "all done with your work yet, darling?"