Fix bug in dynare_estimation_init.m if steady state does not solve

There was no check in dynare_estimation_init.m whether the steady state solved, but the noconstant option was set nevertheless. This gave rise to cases where a steady state file returned 0 for the observables, but the steady state did not exist. Due to later using use_calibration, this problem with the initial values was not detected, but the observation equation featured no constant although it should. The solution is to move the use_calibration option before the first steady state computation and then issue an error if the parameterization does not work