Add simple support for xml output if the third party dict2xml.py module https://pypi.org/project/dict2xml/ is installed. Also this checkin adds the ETag support comment to the CHANGES document. The file was accidently omitted from the rest of the etag checkin.

#!/usr/bin/env python
from __future__ import print_function
import zlib, base64, sys
print(base64.encodestring(zlib.compress(sys.stdin.read())))