HTML Widgets; New widget.UI.FileUpload control

A new FileUpload widget control is now available.

This allows the User to select one of more files (including Resources and Document Manager files) to be uploaded, e.g., to use as File Attachments for an email.

This is used by the new "Send Email Message" wizard HTML Widget.

NOTE: Currently, the file size of "Document Manager" files will appear as "unknown".