More Placeholders for filenames/attachments

There are placeholders which can be used to create a filename for attachments in the sending profile. Eg. Order_Confirmation_{{DOCNUMBER}}.{{EXTENSION}}.

The available placeholders are limited to fields in Structure /conlutio/ms_filename:

This structure should get extend to also allow document or business partner specific fields to be replaced. Examples are:

1. Sales: Customer purchase order number (VBAK-BSTNK)
2. Customer: Shipper's (Our) Account Number at the Customer or Vendor (KNVV-EIKTO)

It would further be very useful if customers could append own fields to /conlutio/ms_filename and to fill them with a new BAdI-Method.