SAK-27871 store reference to assignment in submission object to reduce database calls


git-svn-id: https://source.sakaiproject.org/svn/assignment/trunk@314038 66ffb92e-73f9-0310-93c1-f5514f145a0a
SAK-27865 anonymous assignment performance issue


git-svn-id: https://source.sakaiproject.org/svn/assignment/trunk@314039 66ffb92e-73f9-0310-93c1-f5514f145a0a