Pickled onion munchies... (Additional functional test coverage for fixup)

This change expands the Monster Model so that it:
- Is defined in terms of interfaces with concrete implementations for:
  - Full notification entities (PropertyChanging and PropertyChanged implemented)
  - Entities that only notify for PropertyChanged
  - Normal entities that don't do notifications
- Has additional tests for fixup when FKs change

I did some work to enable the tests for SQLite, but this is currently disabled since Database.EnsureCreated is not working yet.