Support overlay of multiple situations in dynamic graphs when all_situations = TRUE

[sbuis]

• When all_situations = TRUE, curves from all available situations should be displayed simultaneously on the same dynamic plot.
• Each situation should be clearly distinguishable (e.g. via color, line type, legend ...).

[sbuis]

• Set all curves in black by default
• Set different line types (and shape of observations) if shape_sit = symbol