cayenne-lifecycle: @SortWeight annotation

Sometimes it is useful to manually override the operation ordering for some entities. E.g. per CAY-1547 we support UuidRelationships, but saving an object with a UuidRelationship to another object does not generate correct ordering. So we may want to override default ordering for entities annotated with @UuidRelationship. E.g.:

@SortWeight(35)
@UuidRelationship("UUID")
class My extends _My {}

Note that this approach will not be able to address all shortcomings of a generic AshwoodEntitySorter. It is somewhat of a hack. So it will be placed in cayenne-lifecycle and treated as an "extension".