vidya-master-create-exam populating grace period and hard deadline after due date is set
Changing the behavior of when the update happens - only if the grace or hard deadline is before the due date
Implement static page content section reassignment

* Provide the machinery to enable reassignment of the content_section
  while editing a static_page. Care is taken to ensure that when moving
  a ContentGroup parent, it's children move with it.
  (addresses #1819)
Disabling move b/w null content section and not

* The code for moving between the null content section case (like
  Syllabus pages) and the not-null case, and back again, isn't tested as
  well as I like, so this commit adjusts the UI so that users don't
  have that option.
Enforce constraint on course_info pages

* "course_info" pages (those static pages that appear in the top bar
  drop-down) may only ever appear there, where normal pages (those that
  appear in content sections) may only ever appear there.
Make ContentGroup.groupinfo_by_id more defensive
Add checkbox to new announcement form to email to students #1188

Redirects to the email course members page with subject and message
filled with announcement title and description.
Display confirmation message after redirecting to email page
Fix exception from content section move
Merge branch 'master' into jrbl-1819-static-page-section-reassignment_rebase

Conflicts:
	main/courses/additional_pages/views.py
part of #1991, fixes running code for penalites

missing data migration to convert wrong records existant in db
Data migration + 0 -> 0.0
migration has outer loop by exam
constant memory
use Q objects to make queryset smaller
select_related to make less queries
reverting select_related, too memory intensive on staging
select_related on a smaller set--really trying to balance db and memory
Merge pull request #1995 from Stanford-Online/kluo-1188-email-announcement

Add checkbox to new announcement form to email to students #1188
Merge pull request #2003 from Stanford-Online/jbau-penalties-to-float

Jbau penalties to float