Visualisation server gets started even when having no visualisation

[SaMuellerDLR]

When opening a virsat element for the first time from the navigator, the user can feel quite some lag until the editor is open. Apparantly, a major portion of the lag is contributed by the Visualisation plugin getting activated and then automatically starting the visualisation server. This also means loading the libraries for ZMQ and VTK. Some local measurements on my machine, showed that this process may contribute to a lag of ~3s.

The entire machinery with the visualisation server shouldnt be automatically started in projects that dont even use the visualisation concept.