Support camelCase fields (via a json_names option).

[zacharyvoase]

I know this has been asked for a lot, so I decided to implement it. It turns out FieldDescriptorProto already has a json_name for each field, as generated by the protobuf compiler, so this option just causes the compiler to use that (instead of fieldDescriptor.name) for all generated descriptors. Obviously I left in the default behavior of using the names from the proto definitions as-is, for backwards compatibility.

Let me know if I need to add more tests; I wrote a simple smoke test that seems to work though.

[zacharyvoase]

I should mention, this has the benefit that if the proto author overrides the JSON name manually, that will be used. e.g.:

message Msg {
  string a_field = 1 [json_name = "customFieldName"];
}

then the generated JS will use message.customFieldName.

[thesayyn]

Hey. thanks for working on this. I will look into it sometime this week.

[thesayyn]

Looks great! Thanks