Fixed some typos in sample code for writing deep scaline and tiled images

1 - On the page 22 pass arrays as reference:

```
void writeDeepScanlineFile(const char filename[],
                           Box2i displayWindow,
                           Box2i dataWindow,
                           Array2D< float* > &dataZ,
                           Array2D< half* > &dataO,
                           Array2D< unsigned int > &sampleCount)
```

2 - There will be an error at runtime when creating header for deep images with ZIP_COMPRESSION as used by default constructor. Error like this:
"Cannot open image file "deepFile.exr". Compression type in header not valid for deep data"
So, I've changed header initialization to this:

```
    Header header(  displayWindow,
                    dataWindow,
                    1,
                    IMATH_NAMESPACE::V2f (0, 0),
                    1,
                    INCREASING_Y,
                    NO_COMPRESSION);
```

The same on the page 26 for writing deep tiled image.

3 - Changed the indices order to:

```
sampleCount[i][j] = getPixelSampleCount(i, j);
```

 4 - Added the description on the page 25 for the user function: 
"Here, getPixelSampleCount is a user-supplied function that returns the correct sampleCount for each pixel"
as is was done for tiled images.

 5 - Changed the name of the opacity chanel data to dataA for the whole document. Sometimes it was a mess with dataO name.