Process Tree Generator

Draws a random process tree from a parameterised distribution, after Jouck and Depaire's PTandLogGenerator: how many activities, how much concurrency, how many loops, whether there are silent steps or duplicate labels. It is what an evaluation needs that real logs cannot give — a model whose properties were chosen rather than observed, and known exactly before any log exists. Play the tree out and the whole ground truth of the resulting log is known too.