-Move Document_isTargetFormatPermitted from erp5_ingestion to erp5_core to avoid AttributeError when erp5_ingestion is not installed
- Modified Base_getThumbnailAbsoluteUrl so that the absolute_url is only returned when the conversion is permitted in the specified format.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@34136 20353a03-c40f-0410-a6d1-a30d3c3de9de