[Editor] Missing Monobehaviours

[michaelsakharov]

in the Serialize and Deserialize methods on a gameobject we can check if a components type exists, if not Rather than just failing to deserialize that type, we can add a MissingMonobehaviour component instead, and that can store the Tag of the missing component, then we can recover the data if the component resurfaces probably during deserialization of the MissingMonobehaviour

[michaelsakharov]

Their not perfect, some References get lost, but most the settings can be recovered, and asset references also get recovered! :D