add volumes/mount in stack file

[freignat91]

manage volume and mount in stack file per service and add capability to create named volumes used by services (so add a "volumes:" entry in stack file same level than "services:" and "network:"

[freignat91]

Partially done in PR #304, we can now define volumes for services in stack file included named volumes.

[ndegory]

@freignat91 what is missing?

[freignat91]

The capability to create shared volumes in stack files under dedicate topic "volumes" as it's the case for networks

[freignat91]

Close this one, open a new one for the shared volumes