Fixes a long time pending minor issue when deleting downloaded jar files in Windows (were not deleted). Using deleteonexit did the trick, also added verbose to see which downloaded jar files are deleted
So I uncommented the clean-downloads sub-target in the clean-all target
Also adds a description to clean-ivy


git-svn-id: https://svn.apache.org/repos/asf/ofbiz/trunk@1556174 13f79535-47bb-0310-9956-ffa450edef68