Add Notifications for Section Info tool

See the umbrella Jira for this issue:

The Section Info tool should generate notifications when there are changes to the sections or section assignments in a site.

Most of the time, Sections are managed automatically via integration with the SIS. However, if sections are being managed manually, it would be quite useful for students and TAs to receive notifications about changes to sections, such as:

notification sent to student/TA

• students are assigned to a section

• TAs are assigned to a section

notification sent to instructor

• students switch sections

• students sign up for sections