CON-1788 | in-article lists, paragraphs, containers and headers styling ...

...based on grid values
In some places padding / margin values are calculated from variables (``margin-left: $medium-content-padding - $content-border-width;``) and in the others they're hardcoded (``margin-left: 27px;``). I assume that all padding, margin and font size values can be calculated from a few "base" values.