Bug 1171311: Allow group admins to moderate group page comments

As there is already code to verify/submit group page comment
moderation I've added a bit of code to show the private pre-moderated
comments on group pages to group admins so they can moderate them.

Change-Id: Ia117ee00d26c7cf9050345488d65169caff16694
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>