Android coding task: Move part of the logic from Activity to Service to prevent killed

Debugging with an existing Cordova/ Android project, Cordova is only few js logic, main logic is in Android Java.

1. using Vidyo.io video call library
2. the video call library usage is all well tested using in Activity
3. MainActivity will start video call activity
4. But MainActivity launchMode is set to singleTask, the video call activity will be killed after click app icon to resume to app.
5. Moving the video related logic to service, in order to prevent from being killed.