* Removed the *-domain-object collections modules. These are now superseeded by the adt-* modules.
* Removed the deprecated slot indexation.

* This removes the support for the 'unique' tag in the DML language.
* That support was hard-wired in place of JSON tags. Given that very few users (or none) were using the indexes, it made no sense to keep such deprecated code.
* This also impacts the generated code as the lack of that DML construct also means (obviously) that the findBy* methods are no longer generated. The new indexed relations superseed these functionalities.
* Refactored indexes generation that was in the abstract CodeGenerator and moved them to the IndexesCodeGenerator.
* Reviewed all code generators to ensure consistent and correct usage of the DAP Code Generator.
* RelationAwareSet avoids the contains call to the backing up collection.

* DomainBasedMaps now also provide a semantically equivalent add/remove to Set. This avoids the contains method call on the RelationAwareSet when manipulating the collection that backs up the relation, because the collection itself guarantees the semantics of a set.