Add --format to docker version

[phemmer]

Continuation of discussion here and here.

The docker version command should have a --format flag for controlling output. With the formatting change introduced in #10934, it becomes much more difficult to extract a specific field, as each output line does not indicate whether it is for the client or server.
Instead of having to do tricky things with grep awk or other utilities, it would be cleaner to have a --format flag to extract a specific field.

For example:

# docker version --format='{{.Server.GitCommit}}'
0baf609

I think it would also be good to get this implemented before the next release now that #14047 has been merged since #14047 will break any tools that used the previous output format.