"source" property is a counter, "source_trade" is a site: sort out what counter relative url should be built out of which property.
Do not assume billets_mutiles as the destination for banknotes, there is also billets_macules, so look up destination on parent object.
Additionnal sanity checks in init script.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@15310 20353a03-c40f-0410-a6d1-a30d3c3de9de