Bug 1991604: Outcomes portfolio (4) - Adjustments to use the existing signoff...

Bug 1991604: Outcomes portfolio (4) - Adjustments to use the existing signoff switch for activity page

Instead of building a new switch, this patch
- allows the signoff switch to appear on the group -> activity page
- allows the group admin/tutor to have signoff privelege
- have the signoff switch to call new json file instead of normal
signoff json file
- allow group admins/tutors to be able to delete a chekpoint block
- the adding / saving of checkpoint comment returns to the edit pge if
set via edit page
- allow people to edit their checkpoint comment if within 10mins
- stop editing of *_support fields when page is signed off

Change-Id: I260dc4d0c24d7336d230710e8aaf7b87f3600e18
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>