Bug 12110: Display the order vendor note in basket and basketgroup CSV and PDF

Bug 12110: Display the order vendor note in basket and basketgroup CSV and PDF

This bug adds the "vendor note" for each order in the PDF for
basketgroups.  The note is displayed only if it exists, just under the
bibliographic information.

I added a separation line "--------" between bibliographic information
and the note, so that it could be visible at 1st glance.

It also replaces the internal note with the vendor in the CSV for basket
and basketgroup.  It is more logical and useful for libraries to export
the note made for vendor, as those files are destined to be sent to the
vendor.

Test plan :
- fill a basket with some orders, some with internal notes, some with
  vendor notes
- export the basket in CSV : only the vendor notes should be present
- put the basket in a basketgroup
- export the basketgroup in CSV : only the vendor notes should be
  present
- Select "English-2 pages" template for basketgroups in Sysprefs
- export the basket in PDF : the vendor notes should be present under
  the bibliographic information
- Select "English-3 pages" template for basketgroups in Sysprefs
- export the basket in PDF : the vendor notes should be present under
  the bibliographic information

Signed-off-by: Paola Rossi <paola.rossi@cineca.it>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>