Render Definition List as Bullet List

Since not all output format support definition lists, the formatting is sometimes broken.

Therefore we add a switch to render a definition list as a bullet list with definition term and definition data marked as spans.

Since the usability of adjusting the rendering with a macro parameter is low (you have to check the box in every macro), the switch of the rendering mechanism has to be defined as a space property. prentend-being-a requires another value called "printer". There should also be a list of quirk-modes to be applied in this mode. This way an export to PDF could require a quirk mode for the definition list, while an export to HTML does not.