feat(troika-core): add update convenience method to all facades

For usage ala React's setState. Really just a shortcut for assigning
some props and invoking the proper lifecycle responses.

packages/troika-core/src/facade/Facade.js

@@ -65,6 +65,21 @@ export default class Facade {
     this.parent = parent
   }
 
+  /**
+   * Performs a manual update of this facade, invoking the afterUpdate lifecycle method and triggering a
+   * render. This can be called in event handlers, for example, to affect changes to this facade and its
+   * subtree. This process is synchronous. Never override this method as a way to react to updates, as it
+   * is not the only way a component is updated; instead override `afterUpdate` or use setters.
+   * @param {object} props - A set of properties to be copied to the facade
+   */
+  update(props) {
+    if (props && typeof props === 'object') {
+      assign(this, props)
+      this.afterUpdate()
+      this.notifyWorld('needsRender')
+    }
+  }
+
   /**
    * Called at the end of an update batch, after all individual properties have been assigned.
    */