- added: a method to DeviceManager to remove previously ignored objects from the device data 
- changed: StreamImporter->ImportMessageDeletion() excludes a previously ignored object from the device data
- changed: the DeviceManager should always be present when using the StreamImporter. If not, it should be loaded anyway

git-svn-id: https://z-push.org/svn/z-push/trunk@1373 b7dd7b3b-3a3c-0410-9da9-bee62a6cc5b5