Bug 1002247 - [System2] AppAuthenticationDialog fixes

https://bugzilla.mozilla.org/show_bug.cgi?id=1002247

![screen shot 2014-04-27 at 2 37 13 pm](https://cloud.githubusercontent.com/assets/122602/2812382/258d2728-ce54-11e3-93b7-f602f23a1c67.png)