Add support for fetching lightning data

[ASunc]

It looks like fetching lightning strikes doesn't work with metolib. When trying something like this

            var STORED_QUERY_LIGHTNING = "fmi::observations::lightning::multipointcoverage";

            fi.fmi.metoclient.metolib.WfsRequestParser.getData({
                url : url,
                storedQueryId : STORED_QUERY_LIGHTNING,
                requestParameter : "ellipse_major",
                begin : new Date('2015-06-24'),
                end : new Date('2015-06-25'),
                bbox : "20.750000000000014,61.60639637138627,45.00000000000002,66.51326044311185",
                timestep : 60 * 60 * 1000,
                callback : function(data, errors) {
                    handleCallback(data, errors, "strikes");
                }
            });

No data is returned in callback (although server is returning a lot of data). Difference to other multipointcoverage stuff seems to be that there is no target:LocationCollection information in xml, which seems to result in metolib parser ignoring everything.

It would be nice to get this working.