use 'traditional' params in jQuery

For the last (not so) few jQuery versions, a query containing array values (e.g. district=['district1', 'district2']) would get rendered as "?district[]=district1&district[]=district2" when converting data to url format.
In addition, the form parsing won't create an array when only one value is selected, causing parameter name change when the user selects more than one (from district=onlydistrict to district[]=firstdistrict&district[]=seconddistrict).

Setting the 'traditional' parameter to True in $.ajax and $.param makes them behave as before (and works around the bug in form parsing)