[GUI]: Integrated documentation for each scenario element
Currently, one can add a general description of the scenario, and therein, one can describe certain scenario elements more in detail by referring to the related element ids if necessary. This is prone to errors if the element ids are renewed. Instead, one could add an integrated description for each scenario element individually. For example, an explanation could give background information on why source XY spawns 10 instead of 11 agents, or why target changer YZ is needed.