Change List's selectionMode and isAriaListbox defaults

 Tentative fix for https://github.com/ibm-js/deliteful/issues/286:
- change List's selectionMode default from "none" to "single"
- change isAriaListbox default from false to true
- change doc, samples, tests accordingly; in particular, change some samples to use a selection-change event instead of click.

is this fix actually related to selectionMode? Shouldn't this test always be here?