#327 Use Full Compare instead of Hash for Delta Backup

[bugfix123]

Using a hash algorithm for Delta Backup is not safe. A collision can happen which then creates corrupted data. It would be better and safe to use a Full Compare (every byte compared). For slow connections it would be a solution to first make a local (fast) Delta Backup with Full Compare and then make a Standard incremental backup of the just created backup files via the slow connection.