Fix some JSDoc issues

Also makes a few minor changes to the template, so it can be used until
we have a new doc generation process. JSDoc output is written to
build/apidoc.

src/ol/layer/Base.js

@@ -28,7 +28,7 @@ import {assign} from '../obj.js';
  * Abstract base class; normally only used for creating subclasses and not
  * instantiated in apps.
  * Note that with {@link module:ol/layer/Base} and all its subclasses, any property set in
- * the options is set as a {@link module:ol/Object property on the layer object, so
+ * the options is set as a {@link module:ol/Object} property on the layer object, so
  * is observable, and has get/set accessors.
  *
  * @constructor