v1.4.0: Merge pull request #327 from plesk/release-1.4.0

Release Note: Upgrading to the New Version of Leapp Tool

This release includes an important upgrade to the new version of the Leapp tool.
We must switch to the new version because it is no longer possible to install the old version as we previously did.
Additionally, this upgrade should fix some encoding problems related to the leapp pre-upgrade/upgrade commands and in the temporary container.