Fix - psql driver must format qdatetime using iso

QDatetTime must be formatted as ISO8601 specifies, date/month must be padded with 0 until width is 2
Task-number:QTBUG-33389

Change-Id: I2db10e4b0f55a2666b2a12d7d8fcd03f13b96875
Reviewed-by: Lars Knoll <lars.knoll@digia.com>