Remove CheckSum from utils; replace with a TeeReader

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Partition server/ by image, init, events, container, and "everything left"

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Merge pull request #7331 from erikh/simplify_checksum

Simplify utils.CheckSum.Read to use TeeReader instead
Merge pull request #7317 from erikh/server_split

Partition server/ by image, init, events, container, and "everything left"
Add "docker create" support

This exposes the already existing "create container" operation.  It is
very similar to "docker run -d" except it doesn't actually start the
container, but just prepares it. It can then be manually started using
"docker start" at any point.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)

Conflicts:
	api/client/commands.go
	runconfig/parse.go

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: tiborvass)
integration-cli: Add docker create tests

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)

Docker-DCO-1.1-Signed-off-by: Tibor Vass <teabee89@gmail.com> (github: tiborvass)
docs fix

Docker-DCO-1.1-Signed-off-by: Tibor Vass <teabee89@gmail.com> (github: tiborvass)