fix to #5149: 1) 'generator' the base set of relval for generators 2) 'extendedgen' extends the base set to a more thorough assesment of GEN 3) the two sets are exclusive
Merge pull request #5290 from franzoni/remove_duplicates_from-CMSSW_7_2_X_2014-09-13-1400

fix to #5149: 'generator' and 'extendedgen' made exclusive