have favorite group(s) -- feature request #3

Your current implementation sorts groups alphabetically. The pads of the group first in order are displayed per default. I don't want to rename my favorite group (e. g. prefix 1_) in order to move it to the top. Instead I hereby make a wish to have a "star" next to my favorite 1--3 groups I always have to work with, so that their pads are listed per default (and I won't have to click on the group name in order to see the pad names).