Wire RCO texture property to the renderer; fix group parent positions

- Expose the RCO image table as resource.texturetable[label]
- Route native-object property assignment through set<Name>(BaseNativeObject)
  reflection so 'plane.texture = image' reaches PlaneObject.setTexture
- Plane/UButton/Button/Icon draw their runtime texture in preference to the
  static image, and seed the texture property from the static image
- Store the RCO entry's VSMX object so group children inherit parent position

.gitignore

@@ -15,3 +15,4 @@ Thumbs.db
 
 # Disc images
 *.iso
+reference/