Add DB-level onDelete CASCADE example

This adds `onDelete: CASCADE` to the `address` 1-1 relationship just to show how you would map a db-level cascade.
Merge pull request #952 from simshaun/patch-1

Add DB-level onDelete CASCADE example
Merge remote-tracking branch 'origin/master' into patch-1
Typo fix on many-to-many assocaition cascade test