* Adds a static method that copies a collection of EObjects and returns
  a map of all copied elements plus a convenience method that just
  returns the copies of the input elements.
* The new copy method updates references across the given models such
  that they point to the respective copies, which is not handled by
  the standard copy operation. The latter only handles references
  between elements contained in the copied EObject.
* Moreover, bi-references are correctly resolved between the elements
  contained in the given EObjects.

Issue-Ref: 3482
Issue-Url: https://af3-developer.fortiss.org/issues/3482


Signed-off-by: Alexander Diewald <diewald@fortiss.org>