Make quantile plots more accessible by using different marker types

[lembergerth]

The quantile plots that can be created from table-generator use different colors, but the same line- and marker-types for all displayed results.

This makes it difficult for visually impaired users to differentiate the lines.
To improve on this, different marker types could be used for each result.

[PhilippWendler]

Good suggestion!

Unfortunately, it seems that the component we use for showing the lines and markers does not support this out of the box. There is an alternative low-level customizable component with which this is doable, but I am not sure how much functionality of the existing component we would have to implement on our own then. So right now I cannot give a promise for having this implemented soon.

[PhilippWendler]

Blocked by decision on #570.