Streamlined extended paths routines.

*  Removed the  necessity (for  the  user) to  run stoch_simul  bebore
executing the exetended path routine (when options_.init>0).

*  The  value  of  options_.ep.init  defines the  mix  (used  for  the
initialization of  the perfect foresight solver)  between the previous
perfect foresight  solution and  the path obtained  with an  order one
perturbation approach.

* Removed timing related statements.

*  Changed homotopy set-up  for stochastic  extended path:  add future
multivariate innovations one by one.

* Endogeneously increase step_length in the homotopy routine.

* Removed homotopy_2 related code.