code: public void updateApp(int appId, ApplicationUpdate app) {
  		getResourceFactory().getApiResource("/app/" + appId)
  				.entity(app, MediaType.APPLICATION_JSON).put();
  	}
docs: Updates an app. The update can contain an new configuration for the app,
  addition of new fields as well as updates to the configuration of
  existing fields. Fields not included will not be deleted. To delete a
  field use the "delete field" operation.
  
  When adding/updating/deleting apps and fields, it can be simpler to only
  update the app config here and add/update/remove fields using the
  field/{field_id} sub resource.
  
  @param appId
  The id of the app to be updated
  @param app
  The updated app definition