update buildbell.bat file to use gulp

build/BuildBelle.bat

@@ -25,9 +25,8 @@ CD %CD%\..\src\Umbraco.Web.UI.Client\
 ECHO Do npm install and the grunt build of Belle
 call npm cache clean --quiet
 call npm install --quiet
-call npm install -g grunt-cli --quiet
-call npm install -g bower --quiet
-call grunt build --buildversion=%release%
+call npm install -g gulp-cli --quiet
+call gulp --buildversion=%release%
 
 ECHO Move back to the build folder
 CD %buildFolder%