Proxify text_content fields. Deprecate Event_getTextContentCorrespondToFormat (wrong naming, wrong implemetation) and replace it with Event_getEditorFieldTextContent

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@28941 20353a03-c40f-0410-a6d1-a30d3c3de9de