Split Transformation indexation in several activate()'ed chunks

Since the number of possible variations for a resource can be very big,
it is not reasonable to process the indexation of all those lines in
a single big transaction.
Split the process and use activities; one activity per (resource, variation)
couple.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@33435 20353a03-c40f-0410-a6d1-a30d3c3de9de