Add an Upgrade function to migrate version
When dealing with docker and docker-compose, you often want to get your "latest" image up to date.
libre.sh has already an "update" function that "compose pull/del/up"
1- We could also enhance that so any libresh app on the host will be updated ( this could be cronned) , so apps would be always up 2 date
2- the "upgrade" function would take the new branch/tag of the app as argument which would need some logic to find the right variable that contains the app version in the .env ( like NEXTCLOUD_VERSION etc...)