UFABC Library v1.6

This is a stable release which wraps new features and improvements from v1.5 (which was only available for beta testers) and some additional improvements and bug fixes.

What's new:

1. New synchronization scheduler (under the hood).
2. Synchronization is no longer stuck on "infinite loop", since a three minute deadline has been given to the synchronization service execution.
3. Next sync task is performed after fifteen exact minutes if it fails (under the hood).
4. Sync reminder interval defined for each five days (which will be displayed if only it hasn't been synched yet).
5. JavaScript execution call is slightly faster.
6. Books which the devolution is scheduled for the same day are grouped in the same notification.
7. Synchronization settings are updated on preferences change.
8. Synchronization permissions are checked every time the app/service starts so as to check whether the user has revoked them through the device settings or not.

From v1.5:

1. Added activity to visualize lended books when offline (this feature depends on the synchronization service being enabled).
2. Fixed login issues (infinite loop in login screen).
3. Uploaded signed APK (using v1 and v2 signature scheme).