MOF2I2 — ReflectiveSequence is not sufficient - add iterator, remove addAll

Summary:
Martin has proposed adding an iterator operation Iterator and removing addAll.
Iterator would return a ReflectiveIterator that can be used to iterate through all the elements of the collection. If the underlying collection changes while holding an iterator, the behavior of iterator is undefined.

AddAll is useful as an atomic operation. There would be limited value in a language independent iterator – it will tend to make for non-optimal language bindings