[WIP] Add support for Autopilot API

[panaaj]

Add support for Autopilot API.

This PR is to assist in the development of the Autopilot API, specifically for interacting with autopilots via NMEA2000 / SeaTalk.

• Register as autopilot provider
• Action requests via API endpoints.
• Update API with changes originating from autopilot device.
• Update API with alarm notifcations.
• Integrate with NMEA2000 stream events.
• Integrate with SeaTalk stream events.

[panaaj]

@sbender9 This PR adds some initial support for the Autopilot API by:

1. Registering the plugin as an Autopilot provider
2. Defining request handlers that call the existing plugin methods for setting mode, state, target, etc.
3. Establish an N2k stream handler to trigger updates to the Autopilot API for changes in the AP status.

Testing has been via the log files you provided me a while ago.... needless to say I have only been able to test incoming messages and not commands sent to the AP.

As I don't have access to the AP devices supported by this plugin I was hoping you could assist.

The goal is to have a pattern for creating plugins to operate N2K pilots.
I'm not sure the approach I have used is necessarily the correct one so am keen to work through this as required.