- add a line property_movement_group_on_cell on the builder to be able to copy
the reference on cells
- remove my_float_index since the calculation can be done without order

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@27733 20353a03-c40f-0410-a6d1-a30d3c3de9de