AENV-298 - As a publisher I want to configure my Article Edit Screen


- [x] - the width of the viewport for mobile, tablet and desktopview. (pixels)
- [x] - As well as the three diffferent sizes of the images (small, medium, big) applied to the body of an article. (percentage)
- [x] - It should alllow to change the position of the title from 1 to a different position (2,3) in the AES.
- [x] - It should allow to hide/show the standard switches from Newscoop in the switches panel
- [x] - the placeholder text for empty fields should be generic and valid for all type of fields
- [x] - add popovers with the explenation for each setting
- [x] - added setting to change the API endpoint (access can be restricted for this tab for given groups, users)