Calendar rebase

This replaces #1281.

Fixed unit tests and cleaner history based on Scott's rebase. Unit tests work in latest FF and Chrome but still fail via grunt. @jzaefferer You mentioned an upcoming improvement for asycTests?
Ah your right focusable does not support delegation. so `_on` is the best you can do this fixes the problem because `_on` has a built in check if the element is disabled and wont fire any handlers if it is. Also `_on` automatically namespaces the event so you wont need to worry about the `.calendar`. Noticed this when looking into http://bugs.jqueryui.com/ticket/10573