Add the possibility to solve underdetermined models
When the Blanchard-Kahn conditions are not satisfied because the model is underdetermined, it is possible to select a solution among the infinity of solutions, provided we impose more restrictions.
We can implement the solution of Lubik and Schorfheide, “Testing for Indeterminacy:An Application to U.S. Monetary Policy” (AER, 2004), see http://ideas.repec.org/p/jhu/papers/480.html