Handle equality constraints in PSOGA

[marnoldus]

Being able to handle equality constraints in PSOGA will be a large improvement. Currently, metaheuristics for models with equality constraints have trouble converging since they do not find feasible solutions often. The only idea in PSOGA that deals with this is that solutions with a lower constraint violation are preferred. However, this is probably not enough for larger problems.

Possible solutions include repairing the solution after every iteration, after each n iterations or disregarding the equality constraints and repairing after convergence. Another possible solutions is to do some presolve method that reduces the number of equality constraints by transforming them into inequalities.