Massively reorganize and clean up the whole Rust codebase (#478)

* Massively reorganize and clean up the whole Rust codebase

* Additional changes during code review

editor/src/document/overlays_message.rs

@@ -0,0 +1,19 @@
+use crate::message_prelude::*;
+
+use graphene::Operation as DocumentOperation;
+
+use serde::{Deserialize, Serialize};
+
+#[remain::sorted]
+#[impl_message(Message, DocumentMessage, Overlays)]
+#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
+pub enum OverlaysMessage {
+	ClearAllOverlays,
+	DispatchOperation(Box<DocumentOperation>),
+}
+
+impl From<DocumentOperation> for OverlaysMessage {
+	fn from(operation: DocumentOperation) -> OverlaysMessage {
+		Self::DispatchOperation(Box::new(operation))
+	}
+}