Accessor for polygon rings
Make geometries event targets

Previously, the tests were using eql to make assertions about matching geometries.  This is inappropriate for structures with circular references (as with goog.events.EventTarget);
Add setCoordinates for point and dispatch change event
Add setCoordinates for linestring and dispatch change event
Change event for polygons
Listen for geometry events and fire feature events
Listen for feature events and fire layer events
Merge pull request #1096 from tschaub/editable-features

Editable geometries and features.