Move common node creation/editing ui to own function, can edit whole node from creation menu

src/lib.rs

@@ -34,6 +34,12 @@ impl Board {
         });
     }
 
+    pub fn insert_node(&mut self, node: Node) -> usize {
+        let id = self.next_id();
+        self.nodes.insert(id, node);
+        id
+    }
+
     pub fn remove_node(&mut self, id: usize) {
         // We remove this node from the graph, then drop it from each
         // other nodes edge.