Add OO interface to pyobjc-framework-Network

[ronaldoussoren]

Is your feature request related to a problem? Please describe.
Apple's Network framework only provides a C-level API, no classes. It should be fairly easy to expose a more OO interface by adding python-only methods to the exposed classes

Describe the solution you'd like
Use the metadata tooling to automatically generate python_method methods for the various opaque classes exposed in the framework bindings.

There should be a clear mapping between the more pythonic API and the native API (in both directions). Also keep in sync with exposing a more pythonic API for Cocoa classes.

Additional context
This is low priority, and blocked on reworking my metadata tooling.