Provide an interface to fsolve options, in the context of steady(solve_algo=0)

steady(solve_algo=0) uses fsolve to solve the nonlinear system (both on MATLAB and Octave). Only a few of fsolve options can be controlled through the Dynare interface (tolerances and maximum number of iterations).

We should provide an interface for more fsolve options. One possibility is to implement an interface for selected options (one of our institutional partners needs an interface to UseParallel). Another possibility is to implement a generic mechanism, like the already existing optim option of estimation.