Add tilePixelRatio option to ol.source.Tile
Add tilePixelRatio option to ol.source.TileImage
Add tilePixelRatio option to ol.source.WMTS
Add example
Use tilePixelOption in wmts-hidpi example
Add an offset property to ol.Overlay

Replaces "offsetX" and "offsetY" by an ol.Object "offset" property.
Allow the value to be changed while iterating over the rtree
Remove the unused popup from the synthetic-points example
Add docs for tilePixelRatio
Merge pull request #2216 from elemoine/pixelratio

Add tilePixelRatio option to ol.source.WMTS
Merge pull request #2220 from fredj/synthetic-points-popup

Remove the unused popup from the synthetic-points example
Better docs for ol.Overlay#positioning
Make ol.Overlay always call setOffset
Make ol.Overlay always call setPositioning
Merge pull request #2219 from fredj/rbush-update

Allow the value to be changed while iterating over the rtree
Merge pull request #2217 from elemoine/overlay-offset

Add an offset property to ol.Overlay