eachAddonCommand(callback) {
    if (this.initializeAddons && this.addonCommands) {
      this.initializeAddons();
      let addonCommands = this.addonCommands();

      forOwn(addonCommands, (commands, addonName) => callback(addonName, commands));
    }
  }
Execute a given callback for every addon command.
    Example:

    ```
    project.eachAddonCommand(function(addonName, commands) {
      console.log('Addon ' + addonName + ' exported the following commands:' + commands.keys().join(', '));
    });
    ```

    @private
    @method eachAddonCommand
    @param  {Function} callback [description]