CiviReport sent as email via mail_report job with a CSV attachment doesn't show UTF8 characters properly in Excel

Similar to #1424 (closed), if you choose to download a civireport as csv it will now show utf8 characters properly when opened in excel. But that only works for downloads and if you use the mail_report job to send a civireport as an email with a csv attachment, the attachment does not have the BOM.

PR pending but it might be as simple as moving the prepending of the BOM to makeCsv() instead of in the download function, depending on how else makeCsv is used. I already sort of have a test since this came up while writing a test for something.