Implements a feature called quick unlock from keepass2android.
The idea is that generally a long password is beneficial for the security but cumbersome to type every time. As a trade-off keepass2android only needs the full password for the first login. As long as the safe is only locked but not closed, it is sufficient to provide the last n characters of the password for re-entering the safe. If the first try is unsuccessful, quick unlock is disabled until the full password is provided once. I chose n=4. Assuming an alphabet of 26 chars, the chance of a successful guess is at 0.00022%.
This MR also allows using the fingerprint for quick unlock. This should somewhat close #241. The user is guided with a fingerprint symbol stolen from gnome-settings: Animations are also adapted/stolen from gnome-settings. The wiggle means retry, the orange flash means no-match but try again and green obviously unlocks the safe. After two unsuccessful tries the fingerprint turns red and a notification is displayed prompting the user to provide the full password. Kooha-01-20-2022-23-40-40