Maps editor dialog box should have "group" (data) / "groups" (all other modes) field.
- For data mode, the label should be "group", and should allow either nothing, an asterisks *, or a string [a-z]+. Missing, empty, and asterisks value has exactly the same meaning, so it should not be added to the wikitext.
- For regular map modes, the "groups" text field should allow comma-separated entry of group names (must match [a-z]+). Ideally entry field should auto-suggest values defined in the data values (just like Phabricator's "Projects" field, except that it should allow undefined entries).