- the usual adjustments to relationships between inheriting mappers,

- the usual adjustments to relationships between inheriting mappers,
in this case establishing relation()s to subclass mappers where
the join conditions come from the superclass' table
- specifically, places where PropertyLoader limits its search to mapper.local_table had to be expanded
to search separately within mapper.mapped_table as well.  in the case of determining primary/secondaryjoin, it starts more specifically first with local table then out to mapped table if not found.  in the case of determining direction, it starts more generally with mapped table, then if ambiguous direction, goes to the local tables.