Final method2 implementation

Hcal 25ns reconstruction method2 implementation with fast fitter
Hi Chris,

       I would like to know if a direct use of Minuit2 would be thread-safe? I can find a  "ROOT::Minuit2::Minuit2Minimizer" interface to the Minuit2 fit from searching the Minuit2 code. Is this Minuit2Minimizer thread-safe? thanks!

Hongxuan