modify get_take_last_week_for() to return the nominal take
update the tests
modify test to check that the nominal amount is used
Merge pull request #2757 from gratipay/change-take-clipping-algo

Change take clipping algo
Bump version to 16.1.2
Bump version to 16.1.2-dev
simplify functions that take an optional cursor
add a clear_takes() method to Participant

also fixes the 4th item of #2630 (was #1920)
remove obsolete reference in comment
zero out giving/receiving/etc amounts in Participant.archive()
add a fake payday implemented in SQL
make get_tip_to and set_tip_to return a dict instead of only the amount
drop the goal_summary view

We don't use it and its definition is obsolete.
compute giving and receiving amounts more accurately

fixes #1127
fix tests
fix condition
rename function
make tests more thorough
failing test for compute_actual_takes()
fix compute_actual_takes()

Tips are processed before takes, the team giving needs to be deducted from the takes budget.