Adds ability to ignore hacking validations with noqa

Add allownoqa decorator that can be applied to any of the hacking
core functions.  This allows a using application to bypass that
particular hacking validation.  The reason this is being introduced
is because I need to bypass H231 and H233, both Python 3.x
validations.  I need to bypass these so we can run pep8 validations
on the nova XenServer plugins.  XenServer usese Python 2.4 in its
environment and therefore the code won't pass those two or future
Python 3.x validations.

It is understood that a patch to hacking won't be held up or reverted
if it breaks anything Python 2.4 related, including breaking of this
patch.

Change-Id: Iea3867b84212ab30bdd168b5dbd43c11a4dc535e
Merge "Adds ability to ignore hacking validations with noqa"