Pass client to some core functions to make it possible to check
permissions when iterating globals.
Check permissions of factory before using it.
Check permissions in link factory, only allow linking of nodes we can
see.
Check permissions in the autolink module, only try to link to nodes
we can see.
Make client permissions update behave like an atomic update of an
unordered set of permissions, which is perhaps a bit more intuitive.
Add properties to global objects to make it easier to select what
nodes and objects to bind too. They can also be used to implement
permissions on the globals based on properties.
Add more error handling in _register.
Make more functions return a result code.
Make a separate pw_module_register, like all other objects.
Make a link factory and use create-object to make links. That way
we can have different kinds of links based on the factory and we
can also hide the factory when link creation should be blocked.
