Added PermissionLister extension point, enabling permissions to be managed which are not actually loaded.
Failure to unmarshal permission hudson.model.Item.Move
Only display link for Manage Roles where the management of roles is supported by the underlying RBAC configuration source.
Avoid gratuitous synchronization on the root container; it is just delegating everything to another class anyway. More generally, avoid a race condition and improve null safety in case RBAC is turned off in the middle of some operation.