Bug 968677 - [settings] add marionette test for Messaging Settings panel

Could we do 
```
messagePanel.initialMessagingSettings();

messagePanel.enableDeliveryReports();
messagePanel.enableReadReports();
messagePanel.enableWapPush();
messagePanel.enableBroadcast();
messagePanel.setAutoRetrieve('On with roaming');
```
 to instead of the below logic.