Added short explanation file about ContributionTool.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@14172 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/dtml/explainContributionTool.dtml

+<dtml-var manage_page_header>
+<dtml-var manage_tabs>
+
+<p>Explain ContributionTool</p>
+
+This tool is usefull to contribute documents to ERP5.
+
+<dtml-var manage_page_footer>