Add support to set text/uri-list mimedata via setData()

Fixed issue that text/uri-list mimedata got from QMimeData::data()
was corrupted after setting it back via QMimeData::setData()

Change-Id: I2377523a9286519402ab9127ed7f3fa66e39a679
Task-number: QTBUG-45486
Reviewed-by: David Faure <david.faure@kdab.com>