Adds max_child_sortkey to acs_objects, uses select for update to incr tree_sortkey (fixes concurrency problems and substantially improves performance), drop group_elem_idx_container_idx (not useful) and acs_objects_context_object_idx (which is superflous since there is an identical unique constraint). changes acs_objects_get_tree_sortkey to be isstrict/iscachable fixes a bug in acs_objects_context_id_up_tr on both oracle an postgres.