Herwig++.cc: Changed HelperReadInCommandLineParameters to a singleton. In this way its instance and setSearchPath function can be called by HerwigGenericRead function later on. Fixed the problem with my previous commit. -> Still thinking of a way to get rid of the up to now necessary setSearchPatch call in HerwigGenericRead function since HerwigGenericRead function should not depend on command line interface. -> Will be fixed in a new commit