[RocksJava] BackupableDBOptions alginment + 3.8

- Updated the BackupableDBOptions functionality to 3.8.0.
- Aligned Options implementation with remaining source code.
- Invented test-case.
[RocksJava] Backupable/Restorable DB update 3.8.0

- GarbageCollectMethod() available.
- GetCorruptedBackups() available.
[RocksJava] Improved BackupableDBTest

- Splitted methods to meaningful tests
- Added tests for additional functionality
- Covered missing parts
[RocksJava] Cleanup Backupable implementations

- Correct usage of isInitialized()
- Adjusted JavaDoc
[RocksJava] Lint adjustments
[RocksJava] Integrated changes from D29019.
Merge pull request #404 from fyrz/RocksJava-Backup-Restore-3.8

[RocksJava] Update BackupableDB and RestoreBackupableDB to 3.8.0.