nlma for dynare

Dear Sebastien,

Sorry for taking so long. I've tried to reach you by email, but just realized pull request could be a lot more efficient. 

This version of nlma is still in the form of matlab functions, and therefore need to be called after dynare's stoch_simul command. I present this version as I am looking forward to your feedback and advice, before I integrate nlma as an option into stoch_simul.

Thank you very much for your time.

Best,
Hong