Fix #739: tree: make expand return a promise
Improve tree expand promise tests to run fully, and add rejection test
tree: Remove call to _trackError around renderQuery in expand

The call is not necessary because the call to the query inside of
renderQuery is wrapped by _trackError.

The tree-expand-promise test now verifies the error event is being generated
and I added tests for grids that do not have an implementation of renderQuery.
tree-expand-promise unit test cleanup

* Fix typos and assertion phrasing
* Clean out unnecessary this.async usage
* Suppress dgrid-error logging by canceling event
CHANGES.md: Note tree expand method now returns promise
OnDemandList: Skip check in removeRow when justCleanup is true

The check tests if all of the observer's rows have been removed before
canceling the observer, but under normal circumstances OnDemandList will
bulk-remove rows after calling removeRow with justCleanup set to true.
OnDemandList: Add another unit test and remove superfluous assertions

Made the queryRowOverlap non-zero to make sure that it does not affect
the cancelation of observers.
Fix #794: Selection: Prefer pointer to MSPointer events when available
CHANGES.md: Note Selection changes for IE11 / pointer event detection