Bug 27739: Advanced editor should use DefaultCountryField008 preference

Bug 27739: Advanced editor should use DefaultCountryField008 preference

Uses the system preference DefaultCountryField008, falling back to ||| (no
attempt to code) if it is not set, for 008/15-17 place of publication in
the advanced cataloging editor..

Test plan:
1) Apply patch and restart all the things, something's over-cached here
2) Administration - Toggle the preference  EnableAdvancedCatalogingEditor
   to "Enable", verify the preference DefaultCountryField008 is empty
3) Cataloging - Advanced editor
4) In field 008, verify that the three characters after the two sets of
   four blank spaces are |||
5) Administration - Set DefaultCountryField008 to fr
6) Cataloging - Advanced editor
7) In field 008, verify that the three characters after the two sets of
   four blank spaces are "fr " (including the space, so following
   characters haven't shifted left, and the last character is still d)

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>