fgdata/Nasal/canvas/map/VOR.scontroller

# Class things:
var parents = [Symbol.Controller];
var __self__ = caller(0)[0];
Symbol.Controller.add("VOR", __self__);
Symbol.registry["VOR"].df_controller = __self__;
var new = func(model) ; # this controller doesn't need an instance
var LayerController = SymbolLayer.Controller.registry["VOR"];
var isActive = func(model) LayerController.a_instance.isActive(model);
var query_range = func()
	die("VOR.scontroller.query_range /MUST/ be provided by implementation");