Port the IExternalDSEExtensionService to work with the the JavaFX-based implementation of constraint and objective pattern
The retired (but still included) `IExternalDSEExtensionService` was once used to include external patterns in the DSE view. This feature shall be ported to the current JavaFX-based implementation of the DSE view.
(from redmine: issue id 4030, created on 2020-06-16, closed on 2020-08-10)