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/clipboards.rs

@@ -0,0 +1,21 @@
+use super::layer_panel::LayerMetadata;
+
+use graphene::layers::layer_info::Layer;
+
+use serde::{Deserialize, Serialize};
+
+#[repr(u8)]
+#[derive(Serialize, Deserialize, Clone, Copy, PartialEq, Eq, Debug)]
+pub enum Clipboard {
+	System,
+	User,
+	_ClipboardCount, // Keep this as the last entry since it is used for counting the number of enum variants
+}
+
+pub const CLIPBOARD_COUNT: u8 = Clipboard::_ClipboardCount as u8;
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct CopyBufferEntry {
+	pub layer: Layer,
+	pub layer_metadata: LayerMetadata,
+}