Refactor Generated remove*() methods

Done:

* remove*() methods merely mark the record for deletion.
* save() invokes delete() if the record was marked for deletion.
* minimal test cases
* deletion strategy or similar should be used instead of current implementation (update CoughObject::delete())
* if no deletion strategy is present, CoughObject::delete() should throw an exception.
* generator should throw an exception if deletion strategy config is not specified. When specified, appropriate method should be generated in the base/generated class allowing CoughObject::delete() to work without throwing an exception.

Needs:

* more test cases (fully test the feature, e.g. test that it fails when config not set, and test other values like the out-of-box Retire one).