- Assign unique IDs to annotations as soon as the are instantiated (before, annotations relied on the ID-fixup that is triggered when the model is persisted)
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- Keep order of elements to be selected (e.g., EENum values) etc. by using a LinkedHashMap instead of a TreeMap

Fixes a bug in the EStructuralFeatureValueProvider that caused the Enum filter list to be applied on objects that should not be filtered.

Adds the possibility to filter the list of available choices for an enum-type annotation via the annotation's value provider.
Therefore, a map containing the class of the to be filtered model elements and the allowed enum literal must be given in the constructor of the value provider.

DerivedAnnotationValueProviderBase.setAnnotationValue(): Convert String-encoded input to actual data type

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generalize RequirementSpecificationUtils.removeRequirementSpecifications() to 
BaseModelElementUtils.removeModelElementReferenceSpecifications()
  
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Bugfix: Use annotation instance key in setValue(). This is already done in getValue() / getLabel()