[Improvement]: Improve creation of new elements

[mcop1]

Improvement description

Creation of new elements could be improved in several ways

• Is it necessary to set a unique id to the key? If new objects should be created it should be necessary to provide all mandatory fields. Throw an exception instead of adding a auto generated key.
• Add a new operator that auto generates id values, if we really need it. Can then be used to auto generate values for keys to simulate the existing behavior. For this to work we need to change a bit more, for example, we could add a new source field "from operator" in the UI. The user then can select a target field and the unique id operator.
• A flag that indicates if a new object was created or an existing one gets updated. That flag should be available for all operators in the transformation pipeline.

See also #426