added claims, declaration, and other suggestions

[GeorgeKerscher]

suggestions from Gregorio were inserted. I also went through the introduction and first sections and used the word "claims" and "declare" in several places. I did not create a heading talking about claims, and I did not create a note to describe the destinction.

In the conformance the word claims is used. Also, once we have the implementation samples that use the claims or declarations termonology, I think it should be clear.

[gregoriopellegrino]

Two things:

• do we want to suggest that implementers call the section where they will present this data "Accessibility declaration"?
• the conformance section has the word "claim" in multiple places, do we want to leave it in?

[GeorgeKerscher]

We do not yet have our implementation section. I think these will have headings of Accessibility Claims or Declarations. If we want to make this recommendation in the Principles in some other place, I am open to that. That would be for another PR.