Bug 10402 [Template follow-up] Add multiple contacts for vendors

Bug 10402 [Template follow-up] Add multiple contacts for vendors

This template-only follow-up tweaks the button labels and restructures
the vendor view layout a little bit to make it more amenable to multiple
contacts:

- Add spaces after button icons
- Change "Add contact" to "Add another contact" in hopes of making it
  less ambiguous whether clicking it will submit the whole form.
- Eliminate duplicate headers on the vendor view page by making the
  contact name the subheading for each individual contact.

To test, view details for vendors with one or more contacts, and try
editing to add additional contacts. Everything should look good and work
correctly.

Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Signed-off-by: Paola Rossi <paola.rossi@cineca.it>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>