Allowing feedback notifications on group pages (Bug #1307247)

In this patch:
- Changed the Group Edit 'General' section and added the 'Feedback
notifications' options.
- Changed the Group Edit 'General' section and altered the 'Shared
page' option from tickbox to select options.
- Changed the CommentFeedback to be able to notify multiple users in a
group
- Changed the CommentFeedback to be able to send message in the
institution lang if needed.
- Adjusted group_get_editroles_options() to allow it to return a non
associative array

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

Change-Id: Ia2e995c51aa08610945788e55c809b3c650dcd17
Feedback notify emails for institution pages (Bug #1307247)

For institution pages the feedback notify emails will be sent to the
institutional admins - received by institution_and_site_admins()
function (ie the site admins and institutional admins).

I didn't see any benefit of sending it to all institution members so
didn't create the ability to do that.

Change-Id: I76d48f0bc27912f017953063b39c2c47f73ae8e3
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>
Merge changes I76d48f0b,Ia2e995c5

* changes:
  Feedback notify emails for institution pages (Bug #1307247)
  Allowing feedback notifications on group pages (Bug #1307247)