Fix MappingInstantiationException for no default constructor

[hth]

This fixes NO_CONSTRUCTOR issue encountered during Reference instantiation

2:34:22:629 DEBUG o.s.w.s.FrameworkServlet.processRequest Message=Could not complete request
org.springframework.data.mapping.model.MappingInstantiationException: Failed to instantiate org.springframework.social.facebook.api.Reference using constructor NO_CONSTRUCTOR with arguments 
    at org.springframework.data.convert.ReflectionEntityInstantiator.createInstance(ReflectionEntityInstantiator.java:64)
    at org.springframework.data.convert.BytecodeGeneratingEntityInstantiator.createInstance(BytecodeGeneratingEntityInstantiator.java:76)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:250)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:231)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readCollectionOrArray(MappingMongoConverter.java:903)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readValue(MappingMongoConverter.java:1164)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.access$200(MappingMongoConverter.java:78)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter$MongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1115)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.getValueInternal(MappingMongoConverter.java:866)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter$1.doWithPersistentProperty(MappingMongoConverter.java:281)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter$1.doWithPersistentProperty(MappingMongoConverter.java:269)
    at org.springframework.data.mapping.model.BasicPersistentEntity.doWithProperties(BasicPersistentEntity.java:309)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:269)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:231)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:191)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:187)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:78)
    at org.springframework.data.mongodb.core.MongoTemplate$ReadDbObjectCallback.doWith(MongoTemplate.java:2191)
    at org.springframework.data.mongodb.core.MongoTemplate.executeFindMultiInternal(MongoTemplate.java:1873)
    at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:1696)
    at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:1679)
    at org.springframework.data.mongodb.core.MongoTemplate.find(MongoTemplate.java:598)