AUI-1410 - Make aui-scheduler month view accessible

Hi Marc,

Attached is an update for https://issues.liferay.com/browse/AUI-1410.

I had to include commits from AUI-1413 and AUI-1408 so that suff wouldn't break :-/.

The keyboard accessibility is pretty difficult with this module.  I'm not sure a user will be able to figure it out on there own without a lot of instructions.

Please let me know what you think.

Thanks!