Cleanup: server image

This PR removes all the image jobs from server, into graph/. There is one exception: `image_delete` which still has a dependency on the daemon (to be fixed); that has been moved to daemon/.

All this work was done by @shykes. I simply resolved rebase conflicts and migrated tests.

Ping @crosbymichael @LK4D4 @unclejack @erikh
Yup