Adapt to the removal of roboptim::UserIntermediateCallback

Compared to the former version, some elements have been removed:
* the test of RegularMode
* dual_inf, complem, overallError are not stored anymore
Test the mode of ipopt.
Use PostureGenerator::iters_ instead of a local instenciation of the iteration callback to store values.
Also rename IpoptIntermediateCallback in IterationCallback.
Remove all plugin-ipopt linking.