Invalidate on Checked change to force redraw
Invalidate on Checked change to force redraw

- Issue MatterHackers/MCCentral#3047
SliceSettings checkbox fields acting erratically

jlewin/MatterControl,mmoening/MatterControl,jlewin/MatterControl,mmoening/MatterControl,jlewin/MatterControl,unlimitedbacon/MatterControl,unlimitedbacon/MatterControl,unlimitedbacon/MatterControl,larsbrubaker/MatterControl,larsbrubaker/MatterControl,mmoening/MatterControl,larsbrubaker/MatterControl,jlewin/MatterControl,unlimitedbacon/MatterControl,larsbrubaker/MatterControl