Fix Broken Python Data Export

After doing some more testing on the get_read/write_array functions I discovered that they were not correctly representing the layout in memory.

Changes:

Accessing pixel at (X,Y) is now accessed by array[y,x] not array[x,y] (the pixels in each row are contiguous in memory whereas the column data is strided)

The functions now return a slice of the view and now doesn't expose the padded values from the stride. This shouldn't introduce a copy.