Conceptual problem with simple seed

This happened for example with [FBCV](https://github.com/FlyBase/flybase-controlled-vocabulary/issues/71).

There is a definition that contains a foreign term and a relation. Now simple does this:
1. Get all classes in namespace
2. Get all properties OVERALL (in here lies the problem)
3. Removes all axioms that are not covered by 1. + 2.

The problem is that there axioms that contain foreign terms and relations, this relations then make it in the seed, and then are never used; these relations should be filtered out later.