OVT-8464: Added current codes to selectable codes list when adding relations for codeelement.
OVT-8464: Codeelement relation to self prevented.
Fixed Swagger return type for getCodesByUriAndVersion
Raised SLF4J version number to have better log messages. 1.7.7 allows arbitrary amount of {} replacements. Previous limit was 2.
OVT-8464: Added check for parent codes relation when adding relation between codeeelements.
OVT-8464: Fixed tests.
Merge branch 'develop' of https://github.com/Opetushallitus/koodisto into develop

Conflicts:
	koodisto-service/src/test/java/fi/vm/sade/koodisto/service/koodisto/rest/CodeElementResourceTest.java
	koodisto-service/src/test/resources/test-data-multiple-relations.xml
OVT-8464: Fixing tests and test data