* New serialization protos
* Moved old definition to legacy_serialized_data.proto
* defining new serialization format as oneof.
* Changing to legacy datatype
* adding serialization migration
* moving to io
* adding serialization migration
* moving to io
* adding file for test
* adding test
* test for order or migrated serialized data
* test for order or migrated serialized data
* renaming tool
* addressing comments
* addressing more comments
* minor polishing