Ability to add and remove multiple users

Create and delete users. Needed this for a door openener where multiple users would log in, thought you might be interested. Thanks for the great work btw:)
Screen:
![image](https://f.cloud.github.com/assets/294174/1138780/8bbec454-1c7d-11e3-8341-ea31f3bd0d0a.png)