Move Appendix info into main document

Several Appendices would appear better placed in the main document. In MQTT there are only 3 Appendices:

Appendix A. Acknowledgments

Appendix B. Mandatory normative statement (non-normative)

Appendix C. Summary of new features in MQTT v5.0 (non-normative)

I think we should do the same.

Davide already suggested that F.3 should go into the Topic Mapping section.

Appendix C is replaced by the Security Chapter.

Appendix G, Notices, should be at the beginning, like MQTT.

Appendix A References, should be after Terminology.

All of Appendix F should be in the main document or the separate Implementation Guide.

Appendix B should be in section 3 as an optional feature.

Change History goes to Section 1 in the final doc