SAM-2261 Sort by Last Modified column

git-svn-id: https://source.sakaiproject.org/svn/sam/trunk@314889 66ffb92e-73f9-0310-93c1-f5514f145a0a
SAM-1999 Show Last Modified date after import 

git-svn-id: https://source.sakaiproject.org/svn/sam/trunk@314891 66ffb92e-73f9-0310-93c1-f5514f145a0a