Gradient descent and Newton's method for solving convex problems.
Added placeholder for rank_with_grades function
Merge remote-tracking branch 'github/luca' into mshavlov
Merge remote-tracking branch 'github/luca' into mshavlov
grades_rank.py is in
Function for changing all users' passwords is added into maintenance.py
Few fixes.
Another pass on grades_rank.py
Reading db for ranking by grades.
function rank_by_grades is in (without writing to the db).
Few fixes.
get_item samples randomly in half cases. count=min(assigned,1+completed)
get_item. Dont consider submission with n_reject >= 10.
get_item. Now we pay attention how old is a task in progress.
Added simpler way of editing venues.

Conflicts:

	controllers/venues.py
	models/db.py
Many improvements to venue creation and management.

Conflicts:

	models/tables.py
The new venues work, even though not clean implementation.
Much better solution to venue editing.
Finally gotten it to display the email login at the top.
Removed bug in debug print.