Bug 1063041 - Inline the activity options used in the SMS app in order to make it easier to automatically extract the activity arguments from the source code

This ```try``` was used to handle exceptions thrown by ```MozActivity``` constructor. But the only possible case I see is when Messages app is run inside environement where ```MozActivity``` is unavailable (I believe it's only browser for now?). Although this patch changed app behaviour in browser a bit, I don't think it's that important.

So we can just probably remove this confusing ```try\catch``` block and rename ```tryActivity``` to something more appropriate like ```handleActivity``` or anything better you can think of. Eg.:
```
function handleActivity(activity, onsuccess, onerror) {
  if (typeof onsuccess === 'function') {
    activity.onsuccess = onsuccess;
  }

  activity.onerror = typeof onerror === 'function' ? onerror : function() {
    console.warn('Unhandled error spawning activity; ' + this.error.message);
  };
}
```