[ADD] Migration scripts for the project addon

Revert and re-open #65.
Yes this is not very pretty but it is trivial of course:

>>> 'dfsa' % []
'dfsa'

On my initial review I checked that all occurrences I could find in openupgrade-addons/7.0 pass a tuple, not a list. Do you have a concrete example where a list is passed that would trigger a regression?