4169: Allow null data source for OsAccounts and Host Addresses

...ings/java/src/org/sleuthkit/datamodel/AnalysisResult.java

bindings/java/src/org/sleuthkit/datamodel/Blackboard.java

.../java/src/org/sleuthkit/datamodel/BlackboardArtifact.java

...java/src/org/sleuthkit/datamodel/CaseDatabaseFactory.java

...va/src/org/sleuthkit/datamodel/CommunicationsManager.java

bindings/java/src/org/sleuthkit/datamodel/DataArtifact.java

...ings/java/src/org/sleuthkit/datamodel/ScoringManager.java

bindings/java/src/org/sleuthkit/datamodel/SleuthkitCase.java