Update favicon, apple-touch-icon and mstiles

As per #174:

On Apple iOS devices, the boring default icon is shown for SABnzbd in the favourites:
![screenshot](https://cloud.githubusercontent.com/assets/7666402/3755385/a46265e4-1824-11e4-99c9-ac547f312d52.png)
I have regenerated the `favicon`s, `apple-touch-icon`s and created `mstile`s for Windows 8 Metro shortcuts.