[Zope] Disable configuration of 3rd party packages with z3c.unconfigure

[Philipp von Weitershausen]

When relying on a third-party package with ZCML configuration, it is 
sometimes desirable to disable certain directives, for instance when the 
third-party package defines an event subscriber that you'd like to 
disable.  This is now possible with z3c.unconfigure.

While zope.configuration (the package that implements ZCML) itself 
supports overriding existing configuration and the zc.configuration 
package supports excluding whole ZCML files from being loaded, 
z3c.unconfigure allows you to disable specific directives.

More information is available at 
http://pypi.python.org/pypi/z3c.unconfigure.