Zip no compression

Zip folder asynch to the application does not freeze see https://trac.openmicroscopy.org.uk/ome/ticket/11505

To test:
 * Import a single image file. Download it.
 * Import a multi-images files. Download it. A zip should be created.

Check the Download option from the context menu and from the right-hand pane.

The application should not freeze when the zip is created since it no longer happens in the swing thread.

Note that the files are now download in a tmp directory before being moved to the destination selected by the user.
see https://trac.openmicroscopy.org.uk/ome/ticket/11152