Show Doze Mode Warning with Don't Ask Again Option
This MR makes the following changes:
- If Briar is not white-listed, a warning dialog will show after startup
- If Briar comes back after doze and was not white-listed, a warning dialog will be shown
- Both dialogs include a "Don't ask again" option
- Creating an account without white-listing is now possible if the user tries two times
Closes #1103 (closed)