Have resource CRUD return self to simplify the proxies

Instead of:
    def create_project(self, **data):
        obj = project.Project(**data)
        obj.create(self.session)
        return obj

We can:
    def create_project(self, **data):
        return project.Project(**data).create(self.session)

Change-Id: Ifbb41c7d1de461c80ea98b2c3d2e715da770a07f