Bug 938177 - Browser Settings Moved to System Settings

Duplicates browser app's settings in Settings. Browser app is apparently
being deleted, so modifications there likely do not matter.
Nit: you probably want to follow our instantiable pattern found elsewhere in the system app, but it should be easy enough to port after the fact. I won't block the review on it, but let's see what Tim/Alive say.

This would look something like:
```
window.browserSettings = new BrowserSettings();
window.browserSettings.start();
```