Completed FamilyTreeNode, working on FamilyTree.

As I said, I've completed FamilyTreeNode; the node/s that FamilyTree
will hold to keep track of all the members of the family. I've also
filled out a lot of the methods for FamilyTree: you can query the tree
about most family relations. The only methods unimplemented are list
greatNgrandparents/children, and list maternal/paternal lineage. They
should be easy enough to implement, by utelizing the other methods! I
also need to deal with 'step' relationships: right now, the system only
deals with blood relations or adoption.
Most of FamilyTree implemented.

All that's left is listPaternal/Maternal lineage, implementing
step-children, and implementing step and half-siblings. After that, all
that's needed is a bit of clean-up regarding the messages that are
output.