Add the count increment hack to get Observable to recognize the last page
Create unit test suite for testing dojo/store/Observable

This suite generates various test cases involving add, remove, and put
operations across page boundaries on Observable stores.  It includes both
single- and multiple-page cases, and tests with queryRowsOverlap as well.
List/OnDemandList: Use dom.isDescendant instead of offsetParent

offsetParent is problematic in IE < 9.