Render icons on Prefabs

[Fydar]

When the AssetIconAttribute is used within a component that is contained in a Prefab's root-level components, draw a custom icon.

I do have some reservations about poor performance in conjunction with a large number of assets. It might be a good idea to investigate how I can cache the component lookups.

This is a hotly requested feature, however, so I should definitely investigate into this further.