Minor changes and refactoring for psi_pred and psi_truth

Minor changes and refactoring in:
    * structured output machines
    * structured output models
    * CResults structure
to remove result->psi_pred and result->psi_truth
I now see what the problem is.  We need the joint_feature_vector inside the loss function.

Are you sure that this is not breaking PrimalMosek solver?  From what I see, we're introducing big performance penalty for PrimalMosek, because it has to recompute feature vectors in every iteration.

Seems that PrimalMosek forces us to keep the psi_truth/psi_pred vectors?