Add support for Fingerprint sensor for unlocking GnuCash

#### Steps to reproduce the behaviour
1. Open the app (with passcode enabled)

#### Expected behaviour
2. Display homescreen unlock (for pattern input or fingerprint)

#### Actual behaviour
3. GnuCash unlock screen is displayed (no fingerprint support)

#### Software specifications
* GnuCash Android version: all
* System Android version: all
* Device type: all
