Inverting which samples are greyed-out when selected on EMPeror

Hi Darth Microbior :)
On an EMPire plot, I find it counter-intuitive that when brush-selecting a set of samples on EMPeror,
it is the selected samples that are greyed out. Wouldn't it make more sense to have the non-selected samples greyed-out?
May the force-directed graph be with you,
Franck

Start by locating the EMPeror/EMPire brush-selection implementation in the JavaScript visualization code and reproduce the current grey-out behavior. Verify the selected and non-selected sample states, then confirm that non-selected samples are greyed out after the change; add or update the relevant interaction test if one exists.

Written by the indexing model from the issue text.