FIX state change bug (webui#266)

src/main/java/org/caosdb/datetime/FragmentDateTime.java

src/main/java/org/caosdb/datetime/UTCDateTime.java

...in/java/org/caosdb/server/datatype/AbstractEnumValue.java

...main/java/org/caosdb/server/datatype/CollectionValue.java

src/main/java/org/caosdb/server/datatype/GenericValue.java

...n/java/org/caosdb/server/datatype/IndexedSingleValue.java

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

src/main/java/org/caosdb/server/datatype/Value.java

.../java/org/caosdb/server/transaction/WriteTransaction.java

src/test/java/org/caosdb/server/transaction/UpdateTest.java