* protobufjs: updated Message interfaces
* Added ProtoBuf.Util interface
* Fixed load functions of ProtoBuf namespace
Base on the protobuf.js API docmentation.
* use {} instead of Object
Fixed according to PR commit note.
This PR includes the [ProtoBuf.Long](https://github.com/dcodeIO/ProtoBuf.js/blob/master/src/ProtoBuf.js#L19) property. I based the definition on the existing long.d.ts. I didn't use it directly because I didn't want to create a dependency and because the long.d.ts would have to be changed to do this in the first place.
@panuhorsmalahti - does this look okay to you?
