Add update_engine/scripts/payload_info.py

Copied from cros_payload.py, renamed to payload_info.py, removed
dependency on chromite, fixed pylint issues, changed to AOSP license.

usage: payload_info.py [-h] [--list_ops] [--stats] [--signatures] payload_file

Show information about an update payload.

positional arguments:
  payload_file  The update payload file.

optional arguments:
  -h, --help    show this help message and exit
  --list_ops    List the install operations and their extents.
  --stats       Show information about overall input/output.
  --signatures  Show signatures stored in the payload.

Bug: 28797993
Test: payload_info.py --list_ops --stats --signatures payload.bin

Change-Id: Id67a939243fa6ff4a4e9683c7711f71884ee3d6d