add compass module

add a compass module:
![device-2014-08-15-201935](https://cloud.githubusercontent.com/assets/1175520/3935754/6744e7aa-2499-11e4-94bb-607e15f1796a.png)

The compass image is Public Domain (from [here](http://wikitravel.org/shared/File:Compass-icon.svg))

But there's a problem in your loading mechanism. It doesn't detect new Modules, because it just loads the old list from the json settings. Maybe you should just compare the number of loaded modules with the number of available modules and reset if they're not the same.