Feature: Endpoint Registration

This pull request adds the registration and execution of Endpoints. Endpoints are being registered via the Hive. The Hive will then create a registration token, add the Endpoint into the Endpoint Registry, wrap the Endpoint into a Worker, and finally execute the worker.

The Worker will run in a loop, listen for incoming messages, and deliver the messages to its Endpoint. The loop within the Worker will not end until the Worker is terminated. A terminated Worker **cannot be re-started**.

When an Endpoint is being un-registered from the Hive its Worker will be terminated and the Endpoint is being returned to the calling program.