Bug 14769: Introduce Koha::Authority::ControlledIndicators

Bug 14769: Introduce Koha::Authority::ControlledIndicators

This module reads its settings from pref AuthorityControlledIndicators.
The get method allows you to retrieve indicator values for specific
biblio fields.

Test plan:
Run t/Koha/Authority/ControlledIndicators.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Amended: Added a test to show that "ind1:" returns empty string.

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>