CategoryProperty and DynamicCategoryProperty rather than setDefaultProperties
from Utils.

erp5.accessor_holder has also been split up into two additional modules, namely 
erp5.accessor_holder.property_sheet, containing accessor holders for ZODB 
Property Sheets, and erp5.accessor_holder.portal_type, containing accessor 
holders specific to the Portal Types (only being used by PreferenceTool and egov 
for now). erp5.accessor_holder only contains accessor holders common to both 
Portal Types and Property Sheets (such as BaseAccessorHolder).

This commit also enables code committed in r43886.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@43892 20353a03-c40f-0410-a6d1-a30d3c3de9de