[Feature Request] add --all option to docker stop

[fakenine]

Description

When I want to stop all running containers, I have to do a command like this one

$> docker stop $(docker ps -aq)

Proposal

Add a -a, --all option in order to be able to stop all containers in a more simple way

$> docker stop --all

Which would be more intuitive/easy to remember...

I'm willing to work on this one if this is okay.

[collin5]

Or a docker container stop --all. Or both.

[theycallmemac]

I can do the work for this. the stop command requires a container so I'm not terribly sure how Cobra handles that but I'll spend a little time at it all the same.

[theycallmemac]

Just an update, this can work, but I've only gotten it to work by doing this in cli/command/container/stop.go:

Args: cli.RequiresMinArgs(0)

This isn't ideal. Is there any way in which I can do this better?