Create filters in scatterplot

It should be possible to create filters in the scatter plot in a similar way to how it is done in the PCP. If this is done by "drawing squares", then it could be implemented "easily" using the same filter system that is already in place (no new logic needed except for drawing the squares)

Start by locating the scatter plot, the PCP implementation, and the existing filter system. Compare how filters are created in the PCP and determine how square selection in the scatter plot should connect to that system. Done means users can draw filter squares in the scatter plot and apply the resulting filters consistently with the PCP.

Written by the indexing model from the issue text.