Added QR code with API key on Settings dialog

basic stuff... maybe need more polishing (I'm noob with LESS so I added CSS in HTML :) )
![qr_code](https://cloud.githubusercontent.com/assets/108880/4916964/f19284f0-64de-11e4-8914-73f75ece7529.jpg)

```
onsubmit="return false;"
```
I added this to prevent modal closing when enter key is pressed