- By default, EMF uses fragment-path based links to persist EReferences. While this works fine for standalone model resources, it can cause inconsistencies in case there are multiple resource models that contain cross-resource references. (I.e., if the structure of the AF3 model resource changes, the links from the external model resource can become invalid)
- The recommended way to work around this is to configure EMF to use IDs to encode EReferences.

Solution:
- Change persistence of AF3 model resources to encode references using an (extrinsic) xmi:id, that is identical to the model element's org.fortiss.tooling.kernel.model.IIdLabled.id. A dedicated XMIResource type for AF3 model resources is used (which is created by a resource factory registered for *.af3_23 files)
- The reason for not using IIdLabled.id as intrinsic ID is that the implemented solution using xmi:id is both forward and backward compatible
- At the price of losing forward compatibility, the IIdLabled.id could be changed to a derived, volatile EAttribute that simply returns the value of xmi:id
- Add EContentAdapter to sync xmi:id and IIdLabled.id
- Ensure uniqueness of IDs (that is now much more crucial) during when loading and saving as well as importing and exporting models (and print a warning to the console in case duplicates have been detected and fixed)
- As an additional safety layer, add constraint checkers to ensure uniqueness of IDs and consistency of IIdLabled.id and xmi:id

Related changes:
- Speed up loading and saving of XMI resources by setting corresponding XMLResource options
- Ensure that IDs are assigned to annotations as soon as they are instantiated
refs 2309

refs 2289

refs 2140

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- Add Id, version, and ConQAT tags to XML files

* Mainly documentation cleanup
* Remove some commented out code

org.fortiss.tooling.kernel.internal.storage.eclipse.ModelContext:
org.fortiss.tooling.kernel.utils.EMFResourceUtils:
 - Resolve B.19 issue (numbering scheme as of Aug. 14, <https://af3-developer.fortiss.org/projects/autofocus3/wiki/Check-list_for_Code_Reviews/56>) "Use static imports"
refs 2255

refs 2140

SafetyUtils.getParentSpecificationsWithType() --> AnnotationUtils.getParentAnnotationsWithType()

AnnotationUtils: Add TODO to remove workaround that should be no longer required after IDE dev tools update.
refs 2171

a method to determines the {@link EClass} corresponding to a give {@code clazz} (typically the interface for the generated implementation class of an Ecore meta-model).

 - Rename computeFullyName() -> computeFullyQualifiedName()

refs 2093

refs 2093

fix of failures: was again due to the EMF annoying thing of forcing non-duplicates in function arguments
refs 2077

refs 2093

refs 2093

refs 2049

refs 2066

refs 2093

refs 2093

refs 2093

refs 2028

refs 2049

refs 2049

refs 2048

updated the ecore & genmodel models to Kepler (files are strucutrally identical but textually different, hence Eclipse was always displaying local differences)
refs 1868

refs 1943

refs 1980