Cleaning up BackupThread object after use to prevent possible memory leaks
Added client identification to the XML which will be uploaded to the server
backupID has is now from datatype long, using QTemporaryFile for local scheduler.xml, backupStarted.xml and backupEnded.xml
Modifications after reviewing the code with dev-zero
About dialog redesigned

* Removed images from copyright and development company
* Put 'Copyright by' and 'Developed by' on the same line
* Use Sepiola logo if no reseller is set