webadmin: ie10 drag&drop support

DragDropEvent.setData recives two parameters- dataFormat and data.
IE suuports just "Text" and "URL" as the dataFormat (while all the other
browsers support arbitrary string).
In order to support IE the format was changed to "Text".

Change-Id: I5150a6c2b62322969d88d0e2f2a9a85621352d9c
Signed-off-by: Alona Kaplan <alkaplan@redhat.com>