use element mapping to IMG vs. group

I have updated the editors drafts on github for the SVG 2 specification and
the SVG a11y mapping guide to reflect this change, for <use> when
alternative text, descriptions, and tabindex is applied without a role
attribute.

I would like to get a heartbeat draft out for the SVG Accessibility Mapping
specification in August. So far, the changes involve:

- tabindex effecting default role mapping
- For the elements that mapped to none I changed the default mapping to no
mapping at all
- This change

As a minimum,
I would like to see the name computation updated.

If we can be aggressive I would like to see a FPWD of a graphics taxonomy
to coincide with it. I know that is asking a lot, especially, since I go on
vacation again for 2 weeks in July.

Other things to consider:

- ARIA has a good chance of being under a separate charter by August. I
will work with Michael on any logistics involving this.
- Regarding mappings for the new graphics roles, we could put them in the
SVG A!!y mapping spec. and have other specs. map to them.
- Some roles we could place in the main ARIA 1.1 specification if we think
they have broader applicability beyond drawings.
- Defining a prefix of say g- (e.g. role="g-symbol") for the roles in the
taxonomy to ensure no naming conflicts

This is the new module extension process for ARIA 1.X:

https://www.w3.org/WAI/PF/wiki/ARIAExtensions

Thank you for the great call today. We are making a lot of progress.

Best,
Rich

Rich Schwerdtfeger