Import status tb

Indicate in the status of the on-going import in the data manager toolbar.
See https://trac.openmicroscopy.org.uk/ome/ticket/10864

To test:
 * Select few images to import
 * Select an invalid image e.g. Mike.dv
 * Make sure that the spinning wheel is visible during the import process
 * Make sure that the number of failure/success is correct.