UBItem constructor allows $elgg_object as seccond parameter to avoid reloading it unnecesarily
UBItem cloned_from and clone_array now use relationship REL_PARENT_CLONE
UBItem removed delete function in favour of delete_by_id which makes use of elgg's delete_entity (no need to instantiate items)
UBItem get_all function now allows for seccond parameter prop_array to fetch only those properties needed without instantiating full objects