Add hotfixes for varous security vulnerabilities in Plone and Zope

Adds Plone 2011-05-31, 2012-11-06, and 2013-06-18 security hotfixes. All patches apply fine on an empty devel install, except for the 2013-06-18 traverser and wysiwyg patches, which simply throw a warning that they cannot be applied and continues. 

The wysiwig patch does not apply to the version of kupu packaged with Plone 2.5.5.
The traverser patch only applies to Plone 3+.

Also, the Zope2 site has been down all week, so an alternative way to test 5b0c3f2 is to go into the buildout root and run:
`curl http://ftp.jp.netbsd.org/pub/pkgsrc/distfiles/Zope-2.9.12-final.tgz > downloads/Zope-2.9.12-final.tgz`

2.9.12 includes the fix for CVE-2010-1104

I also added a Zope hotfix for CVE-2010-3198