Rust: Add PivImage::combine_bit_planes
Rust: Add PivImage::combine_bit_planes

BitSlice allow us to iterate over the entire bit plane, but
doesn't take into account endianness

The iterator
    0..plane0.len()).map(|x| 7 - (x % 8) + x / 8 * 8)

takes an input
    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
and produces
    [7, 6, 5, 4, 3, 2, 1, 0, 15, 14, 13, 12, 11, 10, 9, 8]

This takes into account the endianness of the input bytes.

joetsoi/moonstone,joetsoi/moonstone