AddObjectsAt x:Int, y:Int, [flags:Str]
Add all ships and planets at a given location to the reference list.
Flags can be a combination of:
- "f" (include foreign ships; default is own ships only)
- "p" (include the planet; default is ships only)
- "s" (include safe ships only; default is also include guessed ships)
- a ship Id (exclude that ship)
See also: Reference List Operations
