Fix layout issues with image captions in wiki

An update of GitLab resulted in new Markdown behaviour for images and captions which results in a messed up layout for our Wiki:

1. a previous release correctly showed image captions below the image in a new line (can be fixed by adding a new line between image and caption text)
2. also the images were shown in a new line (can be fixed by adding a new line between text and image)

Example:

This is an example of a text with an image: And the image caption text.

can be fixed the following way:

This is an example of a text with an image below the text:

And the image caption text below the image