Remove 'valueAsNumber' property from observable list

The property was removed in a0bea641d1fcbec64caf6483c88c9ddb3bea814f
Change ol.dom.Input target param from Element to HTMLInputElement
Add missing function arguments
Listen to 'input' and 'change' events
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
Merge pull request #1696 from fredj/ol.style.image-opacity

Add new opacity property to ol.style.Image
Merge pull request #1724 from fredj/ol.dom.input

ol.dom.Input cleanups