Add visual feedback on how far copying files to and from docker container is going. #1281

Description

I'm copying files to and from docker container to edit them locally.
I would like to see how long it takes, or how many files is there to copy still.
Maybe an estimate how long it takes and how long it has been running copy command.
These could be extra command options you could choose to show the progress of copying files.
It would be useful when you're copying a lot of files.
Expecially it would seem better than what it now is. Currently it looks like the whole console is jammed up when copying because there's no visual feedback of how the copying is going.

Steps to reproduce the issue:

1. copy file to docker container
   docker cp ./www container_name:/var/

2. copy files from docker container
   docker cp container_name:/var/www ./

Describe the results you received:
No visual feedback how far is the copying going. It looks like the console is frozen.

Describe the results you expected:
Some indication of how far the progress is going on with copying files.

Additional information you deem important (e.g. issue happens only occasionally):
visual clue that console is not frozen, that it's still copying files.