FIX: Numerous fixes

This also fix old issues:

* Top border is only the top border of the selected area
  (and not he top border of each cell in the area)
* Same for bottom, left and right borders

Factored out all the border related issues to a new file

webapp/IronCalc/src/components/usePointer.ts

@@ -119,7 +119,6 @@ const usePointer = (options: PointerSettings): PointerEvents => {
 
   const onPointerDown = useCallback(
     (event: PointerEvent) => {
-      console.log("onPointerDown");
       let x = event.clientX;
       let y = event.clientY;
       const {