upgrade plone

#upgrade plone

From the Pleiades 3 proposal narrative, pages 4-5:

Offloading the consumer mission as outlined above will immediately decrease some of the load on Plone, which will continue to provide the interactive editing and reviewing functions essential to the Pleiades publication workflow. By upgrading to the latest version of Plone, we will gain more performance improvements that have been added to the code base since the version we currently use was released.