Fix crc32 computation and increase the image version to 0002

By fixing the crc32 computation, the restoration of previously generated would
fail. The image version is increased to prevent that.

When a version 0001 image is restored, parclone will automatically enable the
option ignore_crc. Since the crc was not correctly generated, there is not
point in checking it.

Signed-off-by: Patryck Rouleau <pfrouleau@gmail.com>