added Feature: output function can now Force a Downloaddialog with DD as the outputparameter, were Firefox Browsers just downloaded the file to the downloaddirectory (when set in preferences)

git-svn-id: file:///Users/Shitiz/Downloads/lssvn/source/limesurvey_dev@7310 b72ed6b6-b9f8-46b5-92b4-906544132732