QTfrontend: Fix flickering and bad offset of control config popup
If you opened the pop-up to change a key, there was a very short flicker at the left side
and the pop-up had a bad offset which sometimes caused entries to be out of screen bounds.
306cedbeb213
fixed several 'retina display' images and added a bunch more (though just from upscaling the normal ones; might be nice to have 'em redrawn at a real higher resolution)
