Allows the user to use `pretty` as the format string.
This enables users to put custom format options into their CLI config
just like is supported for `docker ps` and `docker images`
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Upstream-commit: 54ba82beab8ef8b71f5a6a2f7082ed7759b40df3
Component: engine