Reintegrate the Tutorial Service
In the course of implementing #3922, the TutorialService was disabled
due to strong dependencies in the ContextMenuService on JFace classes.
In order to keep the effort for #3922 reasonable, some of the code
paths were commented out and marked with the ticket id.
The architecture and the class structure should also be reconsidered.
The tutorial service was disabled in #3922 in the RCP, too.
The entry points for reenabling the Tutorial Services are the classes
- ITutorialUIWhitelistProvider (—>see the Deprecated method) and
(from redmine: issue id 4076, created on 2020-10-21)
- relates #3922