Exponentcms Exponent CMS → 2.3.8

We currently use many multiple file download methods/routines, all of which are slightly different, most of which are NOT resume friendly nor low-memory tolerant (crash on large files). We should 'revert' to using a single all-purpose 'download' method/function which adapts to accommodate huge file transfers with resume support. In most cases, this MUST be handled by using a temporary file since 'echo' and other output to stdout tends to buffer the entire file/data-stream before sending (thereby exhausting available memory).

• expController->rss()
• expHtmlToPDF->createpdf() (WKPDF)
• administrationController->export_theme()
• eventregistrationController->export()
• orderController->returnFile()
• storeCategoryController->returnFile()
• storeController->returnFile()
• eventController->ical()
• fileController->export_eql_process()
• fileController->export_files_process()
• expFile->download() ** this should be our main function!
• formsController->export_csv()
• formsController->export_eql_process()
• importexportController->export_process() - generic export method
• reportController->download()