SAK-25734 Refactored to allow integration with an additional calendar tool

git-svn-id: https://source.sakaiproject.org/svn/assignment/trunk@306183 66ffb92e-73f9-0310-93c1-f5514f145a0a
SAK-25734 Changed the word schedule to lower-case to indicate any generic schedule tool

git-svn-id: https://source.sakaiproject.org/svn/assignment/trunk@306184 66ffb92e-73f9-0310-93c1-f5514f145a0a