Insert pasted images as layers in document graph (#1418)

Changes:

Graph is evaluated on every viewport change
move all navigation logic into the viewport
reduce the number of js roundtrips
add canvas rendering
enable image pasting
various cleanups
Fix cache nodes being reset every evaluation

editor/src/messages/tool/tool_messages/path_tool.rs

@@ -393,8 +393,7 @@ impl Fsm for PathToolFsmState {
 				};
 				remove_bounding_box(tool_data.drag_box_overlay_layer.take(), responses);
 
-					PathToolFsmState::Ready
-
+				PathToolFsmState::Ready
 			}
 
 			// Mouse up
@@ -410,7 +409,8 @@ impl Fsm for PathToolFsmState {
 				remove_bounding_box(tool_data.drag_box_overlay_layer.take(), responses);
 
 				responses.add(PathToolMessage::SelectedPointUpdated);
-				}
+				PathToolFsmState::Ready
+			}
 
 			(_, PathToolMessage::DragStop { shift_mirror_distance }) => {
 				let shift_pressed = input.keyboard.get(shift_mirror_distance as usize);