harmonize or add missing CSS classes in markup

[MrTango]

When one want's to style or hide the document byline, she needs to add a lot of CSS to do so for all the templates.
Also the templates often are missing meaningful CSS classes, like "document-byline" to address them easily.
We only have formatting classes from Bootstrap set there and this is wrong.
It is important to allow developers to style elements via CSS, not only by overriding templates!