Uupdate GSL referenece in packaging script.

packaging/nuget/package.bat

 @ECHO OFF
 ECHO Started nuget packaging build.
 ECHO.
-REM: http://www.nuget.org/packages/gslgen
-gslgen -q -script:package.gsl package.config
+REM http://www.nuget.org/packages/gsl
+gsl -q -script:package.gsl package.config
 ECHO.
-REM: http://nuget.codeplex.com/releases
+REM http://nuget.codeplex.com/releases
 nuget pack package.nuspec -verbosity detailed
 ECHO.
 ECHO NOTE: Ignore warnings not applicable to native code: "Issue: Assembly outside lib folder."