SCPgen: Updated step expansion function
SCPgen: combined functions for jacobian and hessian
SCPgen: renamed tan_fcn -> vec_fcn
SCPgen: Changed order of matrix and vector calculation
SCPgen: fixed naming
SCPgen: refactoring
SCPgen: gradient of objective instead of gradient of Lagrangian in res_fcn_ and vec_fcn
SCPgen: Multipliers also for Gauss-Newton
SCPgen: dual infeasibility as stopping criterion also for Gauss-Newton