Gson should support serialization of nulls

[GoogleCodeExporter]

See:
http://groups.google.com/group/google-gson/browse_thread/thread/48a2ce8b9cc2d7ee

We should consider supporting a GsonBuilder mode to send out nulls as well. 

Original issue reported on code.google.com by inder123 on 29 Jul 2008 at 12:30

[GoogleCodeExporter]

Fixed in r126 by providing a GsonBuilder.serializeNulls() option. I also added 
a new
class JsonNull that is used to represent a JsonNull value for use by custom 
serializers. 

Original comment by inder123 on 31 Jul 2008 at 1:51

• Changed state: Fixed

[GoogleCodeExporter]

Added a test for custom serialization using JsonNull in r127

Original comment by inder123 on 31 Jul 2008 at 2:02