Track component selectors in UndoManager. Closes #3879

src/dom_components/model/Component.js

@@ -199,6 +199,7 @@ export default class Component extends Model.extend(Styleable) {
     const comps = this.components();
     if (um && !this.__hasUm) {
       um.add(comps);
+      um.add(this.getSelectors());
       this.__hasUm = 1;
     }
     opts.recursive && comps.map(c => c.__postAdd(opts));
@@ -209,6 +210,7 @@ export default class Component extends Model.extend(Styleable) {
     const um = em && em.get('UndoManager');
     if (um) {
       um.remove(this.components());
+      um.remove(this.getSelectors());
       delete this.__hasUm;
     }
   }

src/selector_manager/model/Selector.js

@@ -21,7 +21,8 @@ export default class Selector extends Model {
       type: TYPE_CLASS,
       active: true,
       private: false,
-      protected: false
+      protected: false,
+      _undo: true
     };
   }