defaultUser.gif to defaultUser.png in Products.PlonePAS 4.0.5. Backport if maurits changes to the trunk svn path=/plone.app.discussion/branches/1.x/; revision=47996
defaultUser.gif to defaultUser.png in Products.PlonePAS 4.0.5. Backport if maurits changes to the trunk svn path=/plone.app.discussion/branches/1.x/; revision=47996