The proxy API is the one that we would like to expose for applications
and the other API is used internally when implementing modules or
factories.
The current pw_core object is really a context for all objects so
name it that way. It also makes it possible to rename pw_core_proxy
to pw_proxy later.
Bind to the resource in create_object before we register the global.
This ensure a client gets to see the resource global id associated
with the resource before it appears in the registry, which makes it
easier to patch the local proxy to the global object.
Metadata allows apps to attach properties to objects that can be
read by other apps.
Not complete yet, properties should be removed when the object is
removed.
