[LMS-2568] improve javadocs

...sd/openbis/generic/server/jython/api/v1/IDataSetType.java

...s/generic/server/jython/api/v1/IDataSetTypeImmutable.java

...eneric/server/jython/api/v1/IExperimentTypeImmutable.java

...eneric/server/jython/api/v1/IFileFormatTypeImmutable.java

...ver/jython/api/v1/IMasterDataRegistrationTransaction.java

.../generic/server/jython/api/v1/IMaterialTypeImmutable.java

...bis/generic/server/jython/api/v1/IPropertyAssignment.java

...ic/server/jython/api/v1/IPropertyAssignmentImmutable.java

.../generic/server/jython/api/v1/IPropertyTypeImmutable.java

...is/generic/server/jython/api/v1/ISampleTypeImmutable.java

...isd/openbis/generic/server/jython/api/v1/IVocabulary.java

...is/generic/server/jython/api/v1/IVocabularyImmutable.java

...openbis/generic/server/jython/api/v1/IVocabularyTerm.java

...eneric/server/jython/api/v1/IVocabularyTermImmutable.java