[Feature] Pass store manager's response to editor's store callback

Hi @artf, We have a need to get a response of the store manager when calling editor.store() method with a callback (we return generated template id in this case from the server). I'm pretty sure you have it implemented for editor.load() method. I think the change is pretty simple in /src/editor/model/Editor.js

/**
   * Store data to the current storage
   * @param {Function} clb Callback function
   * @return {Object} Stored data
   * @private
   */
  store(clb) {
    ...
    sm.store(store, (res) => {
      clb && clb(res);
      this.set('changesCount', 0);
      this.trigger('storage:store', store);
    });
   ...
  },

Let me know if you want me to do a pull request. Thank you.