Automate ObjInterface creation

This fixes DrawInterfaces not having their owner plSceneObject set. It
also makes life easier for when we will export more plObjInterface
subclasses.

korman/exporter/convert.py

@@ -116,7 +116,6 @@ class Exporter:
             ci = self.mgr.find_create_key(bo, plCoordinateInterface)
             so.coord = ci
             ci = ci.object
-            ci.owner = so.key
 
             # Now we have the "fun" work of filling in the CI
             ci.worldToLocal = utils.matrix44(bo.matrix_basis)

korman/exporter/manager.py

@@ -85,7 +85,15 @@ class ExportManager:
                 node.addSceneObject(pl.key)
             elif pl.ClassIndex() in _pool_types:
                 node.addPoolObject(pl.key)
-        return pl # we may have created it...
+
+        # Make life easier for folks creating ObjInterfaces
+        if isinstance(pl, plObjInterface) and bl is not None:
+            so = self.find_key(bl, plSceneObject)
+            if so is not None:
+                pl.owner = so
+
+        # And we're done!
+        return pl
 
     def create_builtins(self, age, textures):
         # BuiltIn.prp