Emulated click events

With this commit `click` and `dblclick` events emitted by the map are emulated events on mouse devices as well. Here are more details on what this commit does:

- `click` events are fired after a 250ms delay, in such a way that no `click` event is fired on double-clicks on the map. Double-clicking on the map zooms the map, so it makes sense that the map doesn't trigger `click` events on double-clicks.
- `click` events are fired only if the mouse action button is pressed. This prevents `click` events from being fired when the middle mouse button is used.
- Without this commit, in Chrome with emulated touch events enabled, double-clicking the map doesn't zoom the map. This is because `ol.BrowserFeature.HAS_TOUCH` is `false` in that environment. The commit fixes that by testing `isMouseActionButton` on mouse devices only.