FIX Privilege escalation through Group hierarchy setting (SS-2013-003)

See http://www.silverstripe.org/ss-2013-003-privilege-escalation-through-group-hierarchy-setting/
FIX Privilege escalation through Group and Member CSV upload (SS-2013-004)

See http://www.silverstripe.org/ss-2013-004-privilege-escalation-through-group-and-member-csv-upload/
FIX Privilege escalation through APPLY_ROLES assignment (SS-2013-005)

See http://www.silverstripe.org/ss-2013-005-privilege-escalation-through-apply-roles-assignment/
3.1.0-rc2 changelog
FIX Disallow permissions assign for APPLY_ROLES (SS-2013-005)

See http://www.silverstripe.org/ss-2013-005-privilege-escalation-through-apply-roles-assignment/
Safety note on DataObject::$validation_enabled