Add detection of canvas line dash support
Use ol.BrowserFeature.HAS_CANVAS_LINE_DASH in ol.render.canvas.Replay
Fix handling of line dash state in ol.render.canvas.Replay
Fix handling of line dash state in ol.render.canvas.Immediate
Merge pull request #1681 from twpayne/line-dash

Fix management of line dash state
Add opacity property to ol.style.Image
Handle image opacity in ol.render.canvas.ImageReplay
Handle image opacity in ol.render.canvas.Immediate
Set ol.style.Icon opacity