Workaround SSL cert issues, enable python 3

Workaround SSL cert issues, enable python 3

 * The script command line switch --insecure added to bypass SSL
   certificate validity checks. Though bypassing is not recommended,
   sometimes the issue can be resolved on the remote side only,
   which we have no control over. For example please see
   https://sourceforge.net/p/forge/site-support/14336/
   The parameter is supported for pythons 2.7.9 and 3.4.3 and newer,
   due to older versions of urlopen do not support context parameter

 * Minor changes allow to run fetch_sources.py under both v2 and v3
   pythons. Changes required due to python 3 prohibits statement-style
   usage for print and forces print statements to be converted into
   functions. Also urlopen() is in library urllib.request in python 3

Components: Framework

VK-GL-CTS Issue #64

Change-Id: If4354332ea19878f8f72352e2df5cac9ee254ac6