prevWife is now an object
Family: add placeholder nodes to the model, so getIndividual() can work on them
Layout: tolerate missing family

When extending the output to include more levels, it's fine that some
branches don't even have a family defined there, while some others do.
Individual: remove no longer needed hasOrderDep

It was a hack, and it seems it's no longer needed. I guess I solved that
problem properly in 3a7e4a4afbe51ff5d3f1157923c0f0bb05763503
(Layout::__buildConnectorSubgraph: make each connector point to the
next/prev node, not to the middle one, 2013-11-21).