Tails launcher

In the networked Tails that journalists use to login to the document interface, each time the connect to Tor they then need to open their Persistent folder and double-click on `securedrop_init` to set up their authenticated hidden services.

I just made a GNOME application launcher that looks way nicer. Instead of `securedrop_init` with a gray generic diamond icon, it's `SecureDrop Init` with SD's logo.

![screenshot from 2014-06-11 19 21 33](https://cloud.githubusercontent.com/assets/156128/3249971/30ac430a-f19f-11e3-85ca-837b3a89c1f4.png)