Bug 1037655 - Move popup icon live preview into a preview icon in the editor 

Changing only this line:
```
iconImg.src = "/src/plugins/popup/images/info.png";
```
to this:
```
iconImg.src = "/src/plugins/popup/images/" + _popcornOptions.icon + ".png";
```
appears to solve the problem. So we might not need the new updateIcon function.