[ENH] Introduce a group blacklist to limit eligible groups

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@50403 b456876b-0849-0410-b77d-98878d47e9d5
[ENH] Administrators should see the goal even if they are not eligible

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@50404 b456876b-0849-0410-b77d-98878d47e9d5