Inconsistent license banners

[Comandeer]

There are two versions of license banners:

/**
 * @license Copyright (c) 2003-2018, CKSource - Frederico Knabben. All rights reserved.
 * For licensing, see LICENSE.md or http://ckeditor.com/license
 */

and

/**
 * @license Copyright (c) 2003-2018, CKSource - Frederico Knabben. All rights reserved.
 * For licensing, see http://ckeditor.com/license
 */

It seems that the first version is used only in presets/<name>-ckeditor-config.js. As we don't have LICENSE.md file in this repo, probably we should stick to the second version.

[mlewand]

Actually the link URL should be changed too as it was moved not that long ago. So that it should link to https://ckeditor.com/legal/ckeditor-oss-license