Bug 26595: Add SMTP server column to libraries table

Bug 26595: Add SMTP server column to libraries table

This patch makes the libraries datatable render the assigned SMTP server
on each row. 'Default' will be rendered when the system default is
detected. A link to the SMTP server config will be rendered when a real
SMTP server is assigned.

To test:
1. Apply this patches, reload al the things
2. Visit the libraries table
=> SUCCESS: There's an SMTP server column displaying the right thing
3. Assign an SMTP server to a library
=> SUCCESS: The table displays the server name as a link
=> SUCCESS: The link correctly points to the SMTP server config page
4. Sign off

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>