Task/pim 1723

Bug fix: no
Feature addition: yes
Backwards compatibility break: no
Unit test passes: yes
Behat scenarios passes: yes
Checkstyle issues: no
ChangeLog updated: yes
Documentation PR: 
Fixes the following jira:
 - PIM-1723

Attribute option fixtures can now be added, in CSV or YAML.
New interfaces were created for entities with unique codes.