bibdocfile: INSERT DELAYED INTO rnkDOWNLOADS

• Switches to INSERT DELAYED queries for entering logging information into the rnkPAGEVIEWS table. We can do this because we are are only logging user download action and we don't need INSERT result to be available in the same session. So let's have DB handle the insert statement when it is free. This can help in improving site response in case of user storms.