Bug 1062798 - Replace custom JSON loaders with LazyLoader.getJSON in Settings App

Replaces custom JSON loaders with the LazyLoader.getJSON helper.
Replaced code in the app permissions, display, help, search and sound panels.
Also replaced within the APN utils module.
As the assertion is in the resolve callback of a promise, when it fails, the exception won't propagate to mocha and which leads to a timeout. To make mocha report the error correctly, we need to do thing like the following:
```
this.mockLazyLoader.getJSON.returnValues[0].then(function() {
  assert.ok(this.mockDisplay.init.calledWith(sinon.match.any, this.mockSensorData));
}.bind(this)).then(done, done);
```