Added default cache objects. A RAM cache for user dependent skins. An anonymous HTTP cache for parts in an ERP5 site which need to be cached and published to many anonymous readers. A global HTTP cache for all skin items which are user independent and should be cached in a front end proxy to reduce the number of request on Zope.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@25287 20353a03-c40f-0410-a6d1-a30d3c3de9de