log-writes: add replay-log program to replay dm-log-writes target

Imported Josef Bacik's code from:
https://github.com/josefbacik/log-writes.git

Specialized program for replaying a write log that was recorded by
device mapper log-writes target.  The tools is used to perform
crash consistency tests, allowing to run an arbitrary check tool
(fsck) at specified checkpoints in the write log.

[Amir:]
- Add project Makefile and SOURCE files
- Document the replay-log auxiliary program
- Address review comments by Eryu Guan

Cc: Josef Bacik <jbacik@fb.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>