Use markers to indicate exit_message in waterfall plot

[FFroehlich]

Would be nice to have this as quick visual inspection

[yannikschaelte]

what precisely do you mean? the exit status somehow plottable on the graph (i.e. whether converged, or out of function evaluations)?

[JanHasenauer]

yes, this would be a nice feature. maybe coloring of points by a exit flag. alternatively the shape might be changed.

[FFroehlich]

https://github.com/ICB-DCM/pyPESTO/blob/808fe96e351864bbed4c977012c2305d029058e8/pypesto/optimize/optimizer.py#L87

I propose to add a way to visualize the message field in OptimizerResult. Currently the clustering information is used for coloring, so marker is probably the thing to go for (could have options to specify what goes where)