Akka.Remote.Serialization.PrimitiveSerializers needs cross platform compatibility

[Arkatufus]

Akka.Remote.Serialization.PrimitiveSerializers breaks when an actor system living inside a .Net core environment sends a remote message to ones that are living inside .Net Framework environment, and vice versa because of the namespace changes introduced between NetFx and NetCore.

Need to change the base class of the serializer to SerializerWithStringManifest to make sure that no future namespace changes will break the wire format again.