Remove false dependencies.
Changed the interface to work with sherpa2. The main changes to previous interface for sherpa2 is the change in the handling of the random nuber engine, here an unnamed namespace is used to store the first reference to the RNG to hand it over to the Sherpa external RNG class
Merge pull request #3469 from alja/from-CMSSW_7_0_3

7_1_X Remove false dependency in  DataFormats/TauReco to RecoVertex/VertexTools
Merge pull request #3474 from degano/sherpa_210_71X

Generators -- Changed the interface to work with sherpa2.
Merge remote branch 'origin/CMSSW_7_1_X' into CMSSW_7_0_X