couple of bugfixes

-fixed screen flickering
-fixed menubar (now works as intended)
-reworked sliders (behaviour more like scrollbars)
-visual fix to dropdowns

source/project/objects/Checkbox.lua

@@ -48,6 +48,7 @@ local function Checkbox(name)
                         end
                     end
                 end
+                self:setVisualChanged(false)
             end
         end;