attempt in LAZY-lize all EAGER loading references for better performance

.../src/main/java/at/tuwien/endpoints/ContainerEndpoint.java

...vice/src/main/java/at/tuwien/endpoints/ImageEndpoint.java

...va/at/tuwien/service/ContainerServiceIntegrationTest.java

...ces/src/main/java/at/tuwien/service/ContainerService.java

...ervices/src/main/java/at/tuwien/service/ImageService.java

...e/src/main/java/at/tuwien/endpoints/DatabaseEndpoint.java

.../test/java/at/tuwien/service/PostgresIntegrationTest.java

...ices/src/main/java/at/tuwien/service/DatabaseService.java

...rvice/src/main/java/at/tuwien/endpoint/QueryEndpoint.java

...ervices/src/main/java/at/tuwien/service/QueryService.java

...vice/src/main/java/at/tuwien/endpoints/TableEndpoint.java

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

...src/test/java/at/tuwien/service/TableServiceUnitTest.java

...ervices/src/main/java/at/tuwien/service/TableService.java