GptPartitionCursor implements the Read + Write + Seek + Debug.

It's used for backing up or restoring partition images, such as in embedded upgrades.

```rust use gpt_partition::Cursor as GptPartitionCursor; use std::io::{Seek, Write};

fn main() -> Result<(), Box>{ let path = "/dev/mmcblk0"; let mut pt = GptPartitionCursor::new(path, "boot").unwrap(); println!("{:#?}", pt);

// Read to boot.bin
let mut fout = std::io::BufWriter::new(std::fs::File::create("boot.bin")?);
std::io::copy(&mut pt, &mut fout).unwrap();

// Write to /dev/mmcblk0p1
let mut fin = std::io::BufReader::new(std::fs::File::open("boot.bin")?);
pt.seek(std::io::SeekFrom::Start(0)).unwrap();
let size = std::io::copy(&mut fin, &mut pt).unwrap();
pt.flush().unwrap();
println!("{:#?}", size == pt.size);

//
// hexdump -C /dev/mmcblk0p1 | head
//

Ok(())

} ```