Add preference of real-time synchronization under setting

Right now, we make the assumption that devices are offline and users need to submit synchronization manually as a batch.

Under setting, we should add options for user preference

• Real-time synchronization (submitted forms will be synced directly to server in real time assuming internet connection is available). If connection is not available, complete form data will be queued up and be synced when connection becomes available later.
• Synchronization on demand (current assumption)