Create a helper library which contains QtRO support code

Introducing the QtRo backend and server autogenerators showed that there is a lot of code which can be made more generic and be reused e.g. connecting QIviPendingReply instances to QRemoteObjectPendingReply and vice versa or the rep files for generic models like QIviPagingModel.

The goal is to create a small private helper library which contains this code and which can be used by the autogenerator or the handwritten services