SDS to SFL conversion script now adds a 'FILE DURATION' field set to 180.  It also replaces periods in column headers with a single space for compatibility with tools designed for SFL files.  Lines for files already encountered are ignored.  Construct an ISO 8601 SFL 'DATE' field from SDS 'time' field.
Added a stronger check for whether 'FILE' field is SDS or SFL style.  Fixed a bug where last column in data lines did not get newline stripped.  Fixed insert_from_command_line function, it was only handling the last line of the SFL file.