1) MouseTracker - Simulated touchenter/touchleave events now bubble to parent element MouseTrackers
2) MouseTracker - Improved multitouch support in enter/exit event handlers
3) MouseTracker - orphaned tracked touch pointers removed (fix for #539)
4) MouseTracker - removed touchenter/touchleave event support since the events don't exist on any known platform and have been removed from the W3C specification
5) Removed Viewer onContainerPress/onContainerRelease handlers (and the associated 'container-release' event ) that were never fired due to the canvas (child) element capturing the DOM events
6) Added 'canvas-enter', 'canvas-exit', and 'canvas-press' events to Viewer
7) ButtonGroup - removed obsolete MouseTracker event handlers
Fix for enhancement #300
Added double-click/tap gesture detection to MouseTracker.with
corresponding dblClickHandler event callback.
Added unit test for double-click detection.
Added Viewer dblClickHandler handling to optionally zoom on
double-click.
Separated event-model/device specific event handling code from
event-model/device agnostic event handling code.
Use enter/leave events instead of over/out events.
Updated unit tests for above changes.
Added unit tests for mouse gestures.
Updated changelog for breaking changes and deprecations.
