Greatly improved table service and test coverage

...tadata-db/test/src/main/java/at/tuwien/test/BaseTest.java

dbrepo-table-service/pom.xml

...ice/src/main/java/at/tuwien/endpoints/AccessEndpoint.java

...rc/main/java/at/tuwien/endpoints/TableColumnEndpoint.java

...src/main/java/at/tuwien/validation/EndpointValidator.java

.../java/at/tuwien/endpoint/TableColumnEndpointUnitTest.java

...java/at/tuwien/endpoint/TableEndpointIntegrationTest.java

...c/test/java/at/tuwien/endpoint/TableEndpointUnitTest.java

...t/java/at/tuwien/gateway/QueryServiceGatewayUnitTest.java

...rvices/src/main/java/at/tuwien/service/AccessService.java

...c/main/java/at/tuwien/service/impl/AccessServiceImpl.java