Updated bitmap (binary/hex) worksheets

I've updated the bitmap (binary/hexadecimal conversion) worksheets. There is now an instruction sheet that contains 5 bitmap grids for students to create their own bitmaps plus 2 grids for them to convert from hexadecimal into a bitmap.

There are also blank worksheets (grids only - no instructions) for 8x8 and 16x16 bitmaps.