Cmssw 7 2 x sherpa 2 1 1

Update to sherpa 2.1.1
Fixes needed for interface to work properly 
Sherpa dynamically loads libraries which are needed at runtime and  looks for them in the location specified in SHERPA_LIBRARY_PATH. Previously we used all libraries in the compilation, thus this variable was not needed.
However, this approach does not work anymore and the authors suggest to only use the SherpaMain library for compilation since (nearly) all needed function are  available from there. The two other remaining libraries (ToolsMath, ToolsOrg) are needed for the external RNG.