Fix#526: Max tiles in rectangular slice
Fix for ticket#526 Remove unnecessary check for number of tiles in rectangular slice. The SliceArgument should be used as max number, not the fixed number of tiles in a rectangular slice.
I also change SliceArgument for example CFG file for RasterScan slice. Currently it is set to 4 but the picture only have 4 tiles which means each picture has only 1 slice. That is not a good example.