SEND-EMAIL view: attachment enhancements

1. add ability to provide alternate name for attachment
2. allow multiple attachments for a single email

Currently the attachment uses the dataset name, which is not always meaningful when working in a non-MF environment. The ability to provide a "PC friendly" name for the attachment would allow the file to be properly handled once received in a non-mainframe email client.

Multiple attachments to a single email would prevent having to send multiple separate emails for each file required to be sent.