Update the PR:
1. Replacing the TFitterMinuit with direct call of TMinuit (new files HybridMinimizer.cc(h)).
   The HybridMinimizer is a copy of the TMinuit2Minimizer with some modification to suit our purpose.
2. Optimization is done in the fit functions to speed up the code. (factor of 4 reduction of CPU time).
3. Many modification to accomodate comments from the PR.