Workbench: better proxy authentication support

git-svn-id: https://svn.apache.org/repos/asf/chemistry/opencmis/trunk@1622634 13f79535-47bb-0310-9956-ffa450edef68
improved error messages

git-svn-id: https://svn.apache.org/repos/asf/chemistry/opencmis/trunk@1622635 13f79535-47bb-0310-9956-ffa450edef68