Function buildExportRequest

Validates the export form and builds the request.

Checks that times and at least one channel are set and that start is not after end. The payload carries the asset, the sorted channels, RFC 3339 start and end, box_id, and a file name made from labjack_name (spaces become _). With filters, the ticked channels that have filters on are sent in filters, so the exporter adds a filtered_value column; without any, the field is left out.