Features/3147 ck editor link enhancement

@donaier @effkay @ryabrody 

Please have a look at my solution for issue #209 

* It is now possible to link via dialogue to other CMS Pages within current locale
* Added CMS pages API. Available under `/:locale/api/pages.json`
* Added link plugin to fetch pages from API

Check it out and holla at me if something doesn't work :v: