1. Provide default methods in proxybase.py for get_<object>_handles and iter_<object>_handles
2. Implement callouts in iter_<object>_handles to determine if handles should be included or not
3. Added new methods to dbbase.py raising NotImplementedError for the new iter_<object>_handles methods
4. Implemented new methods in living.py, private.py and referenced.py
5. Changed filter.py to use iter_person_handles instead of get_person_handles
6. Removed duplicate methods from children of ProxyDbBase
svn: r12783
