Handle fp enrollment errors more gracefully

- When finger can't be analyzed for enrollment
(FINGERPRINT_ERROR_UNABLE_TO_PROCESS), tell the user
to try again or use a different finger.
- When timeout is reached (FINGERPRINT_ERROR_TIMEOUT),
stop enrollment and ask the user to try again.

Fixes bug 23546104
Fixes bug 22708384

Change-Id: I879874b53dd0d928093fab1c92d0d4d68d73be28