Make ol.Feature#setStyle accept `null`
Function circular renamed to createCircularOnSphere
Mark ol.extent.getIntersection as stable
Merge pull request #2726 from elemoine/feature-setstyle

Make ol.Feature#setStyle accept null
Better docs for ol.Sphere#offset
Better docs for ol.geom.Polygon#createCircularSphere
Merge pull request #2728 from tschaub/exports

Mark `ol.extent.getIntersection` as stable.
To do call toLowerCase when forming a change:property event
Merge pull request #2730 from elemoine/tolowercase

Do not call toLowerCase when forming a change:property event
Merge pull request #2727 from elemoine/createcircular

Rename ol.geom.Polygon#circular to createCircularOnSphere