Outplace crossover

[Leative]

Changed the inplace crossover used in SolutionGenerator to an outplace version.
This implies, each crossover operator needs to be applied twice for each pair of parents as well as a fixed arity of 2. Additionally, a contract is needed specifying which of the parents will be used as the result of each step. Currently, the second parent is used as result which follows the idea of parent1 being the source and parent2 being the target of the crossover operator.

Maybe, this should be pulled to an alternative branch?

[alxbrd]

This is an interesting idea, I think we should enable this through a flag somehow in the DSL.

I wonder if there are any performance differences between running the transformation once vs running it twice on individual parents.

[Leative]

What I can tell is that copying the parents is a neglectable effort for models up to model D, taking just a few milliseconds if I remember correctly.

I did not try out comparable rules. Loading the rule models takes some time. But I assume, as long as both rule executions are done directly after each other (so the rules are still in memory), there should not be a difference.

I think, in general, the question is how you can/want to formulate the rules. I would stick to in-place if the situation allows it since it does not require additional rule parameters and might allow for more compact rules.