* add router service polyfill
* add refresh command
* move async code into ember-concurrency task and implement refresh that way
* use ember-concurrency derived state to show a loading spinner when the task is running
* scroll after appending to log too
* remove expanding behavior from engines list and add a configuration route
* use page header component, secret tab component for the template on the secret engine configuration route
* move abstraction to secret-list-header and remove secret-tabs
* add attrs to secret engine model and adjust mount controller code to support that
* fix top level nav so that we can use the back button properly
* fix tests
