Fingerprint [1/2]: Numerous Fingerprint Improvements

1. Introduce getEnrolledFingerprints
2. Introduce Fingerprint object to track name/id/userid
3. Store fingerprints in global settings instead of per user.
   This is because vendor implementations are also global.
4. Give newly enrolled fingerprints a default name.
5. Allow fingerprint names to be changed
6. When getting fingerprint data, merge the native stored fingerprints data
   with settings provider fingerprint data.
   - This is because the vendor will store the actual fingerprint, but all the
     metadata is stored by the provider.
7. Provide basic dump commands in fingerprints

See also:
  libhardware
  vendor specific hal implementation

Change-Id: Iafd2d2f568df5ec1e81f9252a784420ad05bbffe