- self is not the same than context, use context parameter instead
- get closest model from the paysheet
- condition for slice was wrong. if the slice is equal to the base_application, quantity is 0


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@28123 20353a03-c40f-0410-a6d1-a30d3c3de9de