_StoreMixin#_trackError: Avoid leaked global due to context loss

Also, take advantage of single-argument when in 1.8+
Pagination: Fix variable name from merge
OnDemandList: Avoid morphing passed options object
Selection: Refactor unnecessary push calls
Various test cleanup

* Remove unused test/data/colorData
* Use smaller data set for autoheight.html
* Remove references to obsolete results property in dgrid-refresh-complete event
* Remove leftover set('store', ...) call
* Avoid redundant store creation
* Clean up unnecessary dependencies
* Organize _StoreMixin#_trackError unit tests
_StoreMixin: remove event.error.grid property (use event.grid)
CHANGES.md updates/rewording