Set focus to View3DWidget after drag-drop
Set focus to View3DWidget after drag-drop

- Issue MatterHackers/MCCentral#1589

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