added group avatars
Merge pull request #6178 from Popl7/add_group_avatars

added group avatars
Add group avatar to group page. Changed default avatar for group

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
no raw data rendering

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>