minor improvement and cleanup
added option for changing opacity of selected clusters
added user adjustable repulsive force for nodes inside clusters - each cluster has own value
enabled manual insertion in spinbox; set min and max restrictions
removed obsolete gui elements; minor refactoring
added back functionallity to change shapes of clusters (sphere and cube)
partially fixed problem with disappearing nodes and edges inside clusters - they still slightly change color on certain camera angles but at least they dont disappear completely; looks much better now
added option to scale cube and sphere  in each axis - changing it into box(cuboid) or egg shape; improved cube restrictor - which is now in fact box restrictor; some other minor tweaks and cleanups