WIP: versioning phase 8

.../server/database/backend/transaction/RetrieveParents.java

...er/database/backend/transaction/RetrieveSparseEntity.java

src/main/java/caosdb/server/datatype/ReferenceDatatype2.java

src/main/java/caosdb/server/datatype/ReferenceValue.java

src/main/java/caosdb/server/entity/Entity.java

src/main/java/caosdb/server/jobs/Job.java

...in/java/caosdb/server/jobs/core/CheckDatatypePresent.java

src/main/java/caosdb/server/jobs/core/CheckParValid.java

src/main/java/caosdb/server/jobs/core/CheckPropValid.java

...n/java/caosdb/server/jobs/core/CheckRefidIsaParRefid.java

src/main/java/caosdb/server/jobs/core/CheckRefidValid.java

src/main/java/caosdb/server/query/Query.java

src/main/java/caosdb/server/transaction/ChecksumUpdater.java