Action-2036 aria-keyshortcuts

I have updated aria-keyshortcuts to reflect feedback from the group. 

This is the proposal: https://rawgit.com/w3c/aria/action2036/aria/aria.html#aria-keyshortcuts <https://rawgit.com/w3c/aria/action2036/aria/aria.html#aria-keyshortcuts>

What has changed from the last proposal:

1. aria-keyshortcuts is now global so it is not limited to widgets. 
2. aria-keyshortcuts can be use to activate or give focus to elements
3. Fixed inconsistencies in the examples to what we were recommending
4. Pulled back the RFC shoulds and musts on authoring because there are so many keyboard devices out there that trying to address all the permutations really does not belong in the ARIA spec. The responsibility is on the author to address this. We cannot boil the ocean in our spec. This may be something for ARIA authoring practices and we have received great feedback from Apple and IBM that can feed into that. 
5. Made authors aware that they must take into consideration ATs who steal specific keys before they ever reach a web page and key sequences reserved by the browser. 

We will be discussing this on Thursday’s agenda. 

Cheers,
Rich