COMP: Require at least Python 2.6 for Python wrapping

See : http://public.kitware.com/pipermail/community/2014-February/001444.html

I also added a check for the Python executable and library mismatch.

Change-Id: I13927e7339de96e0b7f87f6d76b510c0cdfbe6cc
Merge topic 'Python-versions-release'

0b47ed9f COMP: Require at least Python 2.6 for Python wrapping