Need to correct source reference.

We added the ability to reference the source of something - intended for samples (such as source=hole or source=sample (when comes from another sample).

In the implementation a source reference was included BUT: it allowed any object to be the source. This is not correct as it allowed the object to become a child. The intent was to reference the object, not allow the object to be placed inside the current object.

The consequence was that the entire hole object could be placed within a sample.