Add cli.md documentation for docker-pause and docker-unpause

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
Add cgroups freezer info

Docker-DCO-1.1-Signed-off-by: Brian Goff <cpuguy83@gmail.com> (github: cpuguy83)

Docker-DCO-1.1-Signed-off-by: Brian Goff <cpuguy83@gmail.com> (github: SvenDowideit)
re-jig the info into all the places

Docker-DCO-1.1-Signed-off-by: SvenDowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
Merge pull request #6601 from SvenDowideit/6510-docker-pause-docs

6510 docker pause docs