Setting ASSUME_TARGET_TYPE should allow deserializing objects containing only id

[ledsoft]

When an object contains only id like the following

{
  "@id": "http://example.com/object"
}

JB4JSON-LD assumes it is a reference to a fully serialized object. If it does not find one, it throws an UnresolvedReferenceException at the end of deserialization. However, when ASSUME_TARGET_TYPE is set to true, it should be possible to use such objects and deserialize them as objects of the target type having only identifier set.

To prevent interference with the reference resolution algorithm, these objects should be created only after all references are resolved and there still remain potential pending references.