Merge pull request #7449 from shykes/cleanup-shutdown

Cleanup: refactor shutdown and signal handling facility
Move "pull" and "push" to graph/pull.go and graph/push.go

This is part of the ongoing effort to remove the deprecated server/
package, and generally cleanup and simplify the codebase.

Signed-off-by: Solomon Hykes <solomon@docker.com>
Move "build" to daemon/build.go

Signed-off-by: Solomon Hykes <solomon@docker.com>
Remove deprecated server/ package

Victory!

Signed-off-by: Solomon Hykes <solomon@docker.com>