Define experiment constants as list of values

[merkste]

Prism already allows to define the values of a constant an experiment iterates over as a range, e.g., -const "a=1:10:2". It would be convenient to allow the user to simply list the values he's interested in, too. Of course, command line syntax has to be considered here, for instance -const "a=1;2;3;5;8;13", and input via the GUI, too.