Operator panel: Enable editing 2D operator panel elements and test simulation
Problem
- Currently, only the "3D Viewer" and the "Graph Viewer" elements can added (from the model navigator's context menu) or the "Model Element Library"
- 2D elements such as "Label", "Push Button", ... are shown only in expert model in "Model Element Library"
Expected behavior
- Elements are offered also in non-expert mode
- Simulation behavior elements is verified, e.g. by extended the "operator_panel_tutorial" from the file menu