Formalise plugin schemas

[oliverfoster]

Subject of the issue

Document available for comments, Schema Processing Outline and Future Direction

[oliverfoster]

We just need documentation for how the new schemas work and this sorted innit? @taylortom

[taylortom]

Yep, lemme know what I need to do here :smile:

[oliverfoster]

I think we neeeed... (update if you think of anything else, and probably not in this order for the final documentation)

• Header definition
• Property definitions
• Spec conformity
• Additions
• Inheritance/extension rules
• Differences to old schemas / how to migrate

[oliverfoster]

Implemented in AAT v1