Override onBackPressed() and prompt user before exiting from App

[f-odhiambo]

Desired Feature Override onBackPressed() and prompt the user before exiting from the App

1. onBackPressed() prompts the user if they want to Quit the application if on the Homescreen
2. If in a given workflow, navigate through the back stack to the home screen then prompt the user to exit the app
3. This should also be reproduced whether you use the physical back button or on the top bar navigation back button icon

Acceptance Criteria

• [ ] For previously navigated screens traverse back the back stack list else if no home then exit the app after the prompt
• [ ] Make the on-back press text prompt translatable in the build variant string.xml file