zb: Add ObjectServer::request_name

Since typically a well-known name is registered by services, it makes sense to provide the most convenient way to register it. Theoretically this should be a method of Connection but there is a very real a danger of users registering their name before creating the ObjectServer instance and as a result, missing out the first method call (e.g in case of D-Bus autolaunch).

The method uses the builder pattern as typically this will be used when instantiating ObjectServer.

Fixes #114 (closed).