Add more content for the API doc

Involves additions to (there will be subsequent pull requests for other
classes):
- ol.Attribution
- ol.Collection
- ol.Expression
- ol.Feature
- ol.Geolocation
- ol.Map
- ol.Object
- ol.Overlay
- ol.Projection
- ol.View2D
- ol.control.Attribution
- ol.control.Control
- ol.control.FullScreen
- ol.control.Logo
- ol.control.MousePosition
- ol.control.ScaleLine
- ol.control.Zoom
- ol.control.ZoomSlider
- ol.dom.Input
- ol.filter.Filter
- ol.filter.Geometry
- ol.filter.Logical

src/ol/control/scalelinecontrol.js

@@ -30,6 +30,18 @@ ol.control.ScaleLineUnits = {
 
 
 /**
+ * Create a control to help users estimate distances on a map.
+ *
+ * Example:
+ *
+ *     var map = new ol.Map({
+ *       controls: ol.control.defaults({}, [
+ *         new ol.control.ScaleLine({
+ *           units: ol.control.ScaleLineUnits.IMPERIAL
+ *         })
+ *       ]),
+ *       ...
+ *
  * @constructor
  * @extends {ol.control.Control}
  * @param {ol.control.ScaleLineOptions=} opt_options Scale line options.