As a Brown Dog Administrator I want to be able to edit existing bindings for an exchange so I can change which extractors/converters are notified.

Acceptance Criteria

1. Existing bindings from RabbitMQ are shown in the binding editor dialog window.
2. Click off an enabled binding
3. Click on a previously disabled binding
4. Save bindings
5. Deselected bindings have been removed
6. All selected bindings are enabled in the exchange