Upgrade script and deployment files to upgrade the database
from version 3 to 4.
Also, upgraded the database schema version to version 4.

To create these deployment files one has to change
the schema version in lib/OpenQA/modules/Schema/Schema.pm
and then run: ./upgrade.pl --prepare_upgrade
(Don't forget to commit those files to git)

Once the deployment files are created, to upgrade a database
the following command has to be run: ./upgrade.pl --upgrade_database