Service annotator should annotate private services

[stof]

As the plugin is able to find private services now, it would be useful to have the annotator applied for their classes as well, to jump to the service definition

[Haehnchen]

u mean a gotoprovider or a referencecontributor :)
by now only classname (string-set) is indexed for more we need a custom dataindexer. also for #77

[stof]

I mean the annotator adding an icon near class names to go to the service definition (which is already available for public services)

[Haehnchen]

nevertheless, if we get one we will get all :)