Use UUIDs to identify types

Right now we use the user-provided names for Resources/Components to identify them when deserializing update data sent from the editor. While this is an *okay* solution in the short term, we'll need a more stable way of identifying types in order to support prefab editing in the future. To do this, we can use [serde-dyn](https://crates.io/crates/serde_dyn), which provides the trait [`TypeUuid`](https://docs.rs/serde_dyn/0.1.0/serde_dyn/trait.TypeUuid.html).

> TODO: Note that we'll have to define our own `TypeUuid` trait because of the orphan rule.

> TODO: Note that we should put this behind a feature until we're ready to make it mandatory.