Calling SteamVR_ControllerManager multiple times adds multiple instances of left/right

[aleiby]

Maybe use HashSet to avoid duplicate entries when updating this.objects.

[aleiby]

This should also fix the double hide issue.

Repro steps:

• Attach both controllers in Steam VR_Controller Manager in the named slots ('Left' and 'Right')
• Attach both controllers in Steam VR_Controller Manager to the 'objects' array
• Start the app and hit the Steam Menu button to get to the Steam Menu
• Hit the Steam Menu button again to exit back to your app -- your controller models have now irreversibly disappeared

The issue comes that the controller gameobjects under CameraRig are hidden twice if they exist in both Left/Right and 'objects', but only unhidden once. Hiding consists of creating a new GameObject called 'hidden' and making it a parent of the controller gameobjects, and is presumably done somewhere within the SteamVR plugin.

[aleiby]

Fixed in next version.