Allow upgrade for old version

[BenoitCier]

Problem

• Can't upgrade from old version of the package Issue #46

Solution

• upgrade backup script

PR Status

• [x] Code finished.
• [ ] Tested with Package_check.
• [ ] Fix or enhancement tested.
• [x] Upgrade from last version tested.
• [x] Can be reviewed and tested.

[BenoitCier]

!testme

[yunohost-bot]

:v: