Feature request: visual indication of keyboard sample slot state (loaded/playing)

[mxmilkiib]

Two things it would be handy to see from a glance - which sample slots are empty and which are playing. Maybe if the background of the key on the keyboard display could change to an alternative colour when its sample is a) loaded, and b) playing?

[milasudril]

Other alternatives include using slanted or boldface text. It does not collide with the color chosen by the user.