feat #1137 add tests for util.Dom.getGeometry
fix #1137 utils.Dom.getGeometry on absolutely positioned parents

This commit fixes some of the issues in Dom.getGeometry method:

- it adjusted the returned value only on elements with overflow scroll or
  auto, and not when overflow was hidden
- when an element had absolutely positioned ancestors, it was returning
  incorrect values (due to the fact that a parent of absolutely positioned
  element has computed height of 0); particularly it was sometimes wrongly
  returning null while the element was visible in the viewport
- it was sometimes doing calculations unnecessarily

The original issue which triggered the investigation was about SelectBox
inside absolutely positioned parent not displaying the dropdown due to the
call to getGeometry returning null.

Close #1140.
fix #1135 loading indicator scroll issue in IE8-

In IE8 and IE7 the scroll event does not bubble up, so the loading indicator refresh is not triggered when the user scrolls a view inside a container.
This fix registers listeners on the ancestors of the overlayed element (only for IE8 and below), and adds 2 new util methods in aria.utils.Event
fix #1053 update textcontent of Text widget on bound property change

Close #1141