Bug 9782: hide cancel button when importing MARC bibliographic frameworks

Bug 9782: hide cancel button when importing MARC bibliographic frameworks

When importing frameworks the "cancel" button should be hidden once an
import is initiated since it is not possible to cancel the import in
progress.

This patch uses this bug as an excuse to replace the old import/export
pop-ups with modal dialogs for all import/export functions.

To test:

- Try exporting both the default framework and at least one other
  framework.
- Try importing both a default framework and at least one other
  framework.
- When importing, observe that the modal dialog controls are hidden as
  soon as the import is initiated.

Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Works nicely, passes all tests and QA script.
Also the modal works better on smaller screens.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>