* DynamicTreeViewers and alike are often used for a specific set of base
  types. Thus, generics can be used to reduce the code by subclassing
  these controls for specific meta-model types like IHierarchicElements.
* Second, a bit more type-safety is achieved without sacrificing
  ease-of-use since the controls can still be constructed for Objects
  for complex object relations.

Issue-Ref: 3209
Issue-Url: https://af3-developer.fortiss.org/issues/3209


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