Remove getBusinessProcessValue since this makes no sense in the context of multi BPM. It is redundant with asComposedDocument and/or asUnionBusinessProcess

git-svn-id: https://svn.erp5.org/repos/public/erp5/sandbox/amount_generator@36053 20353a03-c40f-0410-a6d1-a30d3c3de9de