Update CKEditor website links

[mlewand]

After our recent CKEditor website update some links got outdated.

For instance, in the toolbar:

• CKEditor API - links to http://docs.ckeditor.com/#!/api, should be https://docs.ckeditor.com/ckeditor4/docs/#!/api
• Documentation - links to http://docs.ckeditor.com/#!/guide, should be https://docs.ckeditor.com/ckeditor4/docs/#!/guide