New Stacks config option: remove volumes on stack stop

[matthewGEA]

This feature request is to add a configuration option within the Stack Editor to allow the equivalent of the "-v" flag for docker-compose down:
Remove named volumes declared in the volumes section of the Compose file and anonymous volumes attached to containers.
https://docs.docker.com/compose/reference/down/

When starting a stack on a standalone system, a container can be started without any volume mappings which will result in anonymous volumes being created.

Each restart of the stack will create new anonymous volumes, leaving the old ones as "unused". Currently, a user must go in and manually prune the unused volumes.

[kevinholtkamp]

Another use case for this: I use CIFS mounts for all my volumes. When I change something in the options of the volume mounts, I have to manually remove the old volume so that one with the new configuration gets created.

Especially useful in swarm mode, when you can have different "versions" of mount options on different nodes