+ this allows to remove CLHEP dependency in NPLib
   + this allows to remove Constant.h file

 - Try as an absolute or relative path
 - if fail try in the standard location
 - if fail exit with error code 1

 - Renaming of private member of Initial Condition
 - Beam energy was not set in Read Configuration

 - fixing couple of bug
 - remove some warning
 - enhance performance

 - Only one read configuration file method
 - lighter code
 - possibility to use TH1F for cross section shoot

 - Add associate class in NPL
 - Add Function in NPL

Some code clean up has been done as well (cosmetic change for the most)