Drag to rearrange layers in the layer panel (#434)

* Add insert line

* Implement dragging

* Improve CSS and variable naming consistency

* Resolved folder crash, added Undo/Redo support

* Removed marker TODO leftover

* JS cleanup

* WIP preserving expanded state (via LayerData) when copy/pasting and moving layers in layer panel

* Finish making folders copy/paste preserving expanded state, but not recursively yet

* Add cut, copy, and paste to the Edit menu (#440)

* Add cut

* Hook up edit dropdown

* Use copy message

Co-authored-by: Keavon Chambers <keavon@keavon.com>
Co-authored-by: otdavies <oliver@psyfer.io>

graphene/src/operation.rs

@@ -76,9 +76,9 @@ pub enum Operation {
 		path: Vec<LayerId>,
 		name: String,
 	},
-	PasteLayer {
+	InsertLayer {
 		layer: Layer,
-		path: Vec<LayerId>,
+		destination_path: Vec<LayerId>,
 		insert_index: isize,
 	},
 	CreateFolder {