rest of virtuals removed

virtuals removed and replaced with override where necessary on the rest of the code base, clang-tidy to the rescue.

Engine/source/gfx/bitmap/imageUtils.cpp

@@ -78,7 +78,7 @@ namespace ImageUtil
          : pSrc(srcRGBA),pDst(dst), width(w), height(h), format(compressFormat),quality(compressQuality) {}
 
    protected:
-      virtual void execute()
+      void execute() override
       {
          rawCompress(pSrc,pDst, width, height, format,quality);
       }