distinguish accessibility from reusability

[cmbarton]

Some of the text in the accessibility goals document actually refers to reusability and is better moved to that document

[alee]

This is mostly done, though I find that the current OMF Accessibility Standards roll together Findable and Accessible from the FAIR principles based on my understanding. Perhaps we should make that more explicit?

There's a bit of an implicit understanding from the text that what we consider to be an Accessible OMF model is that it must be made available over HTTP/S on a permanent web landing page with metadata about the model and links to download the model in a form that's amenable to local execution (or links to run the model on the cloud).