Column replacement, if the stack matches from its base.
Polymorphic test.

No code to make it work yet, mind you.
Don't include columns for tables that don't have them.

Only crops up in polymorphic situations.
Polymorphic support

But only when you specify the polymorphic association in the index definition.

Seriously needs some refactoring, and unrelated tests are now failing as well.
Happier tests for associations and property presenter.
Syntactic cleaning.
Splitting Polymorpher in two, and adding unit tests.

Still room for improvement - perhaps with inner classes to start with - but this is certainly cleaner than what came before.
Noting polymorphic support for index definitions.