Bug 20144: [sql_modes] Add default values for export_format columns

Bug 20144: [sql_modes] Add default values for export_format columns

Fix for:
Field 'field_separator' doesn't have a default value
Field 'encoding' doesn't have a default value

field_separator and subfield_separator are only used for MARC csv
profiles, no need to specify a default value

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>