Pickled onion munchies...

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.
(This is the ALTER TABLE ... ADD FOREIGN KEY issue I'm currently working on.)