Revert "Add autoFetch === 'onRead' functionality to RelatedArray."
This was too immature and will take lots more work.

This reverts commit 2d5d4a32235b5cb18ab9af7a47f8507fbd830490.
Revert "Add autoFetch === onRead option to fetch RelatedModels only when accessed."
This is too immature and will need much more work.

This reverts commit 92471cae7bc0c6c4388a3ac5e7d181d7a26d3fc2.