Add delete undo styles

This is much like Android's undo delete for notifications and mails and allows you to undo a deletion of a menu entry:

![deleted](https://cloud.githubusercontent.com/assets/195053/4167528/271b6f10-3514-11e4-9e0d-f3a68dc3df41.png)

by using this html:

```html
<div class="app-navigation-entry-deleted">
    <div class="app-navigation-entry-deleted-description">Deleted feed Bild.de</div>
    <button class="icon-history" title="Undo"></button>
    <button class="icon-close" title="Remove notification"></button>
</div>
```

The history button undoes the deletion, the close button gets rid of the message

@jancborchardt @jbtbnl @MorrisJobke @georgehrke @raghunayyar @LEDfan

Please also review the design and workflow.