Add test for JAVA-509

So far, the test fails with a NPE:

```
java.lang.NullPointerException
	at com.datastax.driver.core.querybuilder.Utils.appendName(Utils.java:289)
	at com.datastax.driver.core.querybuilder.QueryBuilder.quote(QueryBuilder.java:231)
	at com.datastax.driver.mapping.EntityMapper.getKeyspace(EntityMapper.java:48)
	at com.datastax.driver.mapping.UDTMapper.<init>(UDTMapper.java:44)
	at com.datastax.driver.mapping.MappingManager.getUDTMapper(MappingManager.java:138)
	at com.datastax.driver.mapping.ReflectionMapper$ReflectionFactory.createColumnMapper(ReflectionMapper.java:364)
	at com.datastax.driver.mapping.AnnotationParser.convert(AnnotationParser.java:153)
	at com.datastax.driver.mapping.AnnotationParser.parseEntity(AnnotationParser.java:102)
	at com.datastax.driver.mapping.MappingManager.getMapper(MappingManager.java:119)
	at com.datastax.driver.mapping.MappingManager.mapper(MappingManager.java:76)
	at com.datastax.driver.mapping.UDTFieldMapper.stuff(UDTFieldMapper.java:42)
[...]
```