Fix bug in 'ModelFitting.convert_to_parameters'
Method ModelFitting.convert_to_parameters
modify its input parameter.
It's a serious potential bug, because it can influence Pygmo's output
Example:
>>> model_fitting = ModelFitting(...)
>>> decision_vector = np.array([...])
>>> copied_decision_vector = decision_vector.copy()
>>> parameter_vector = model_fitting.convert_to_parameters(decision_vector)
>>> np.testing.assert_equal(decision_vector, copied_decision_vector)
AssertionError: ... # decision_vector is modified !
Edited by Frederic Lemmel