Working Process.test_dependency_constraints: apply recipes equations + minors.
Done: - apply recipes equations in Constraint_system.apply_recipe_subsitution
      - fix a test in Process.test_dependency_constraints
-> bench for 7 parallels: 0.37s instead of 38.41 s
Todo: - allowing New, In and Out at top level (starting compression+reduction
        after a prefix of New,In,Out)
      - automatize benchmarks