Precise-->Trusty patches for several guides

As Juno will not be supported on Ubuntu 12.04 Precise,
this patch changes all references to 14.04 Trusty, which will
support the next 4 releases.
Updated section_ubuntu_example.xml for consistency.

Change-Id: Ib52513db38b17240026e6a278e8c97c0438358ec
Merge "Precise-->Trusty patches for several guides"