PyUT: Add initial unittest framework, limit possible python versions to >= 2.7.

PyUT: Add initial unittest framework, limit possible python versions to >= 2.7.

Limiting the supported python versions to >= 2.6 permits to avoid unneccessary
code to permit the use of unittest in all python 2 and 3 versions such as:

import sys

if sys.version_info[0] >= 3:
	import unittest
else:
	import unittest2 as unittest

python2.7 is the default version in Debian unstable since Sep 2011.