Checking project deadline should always call has_deadline_passed

[Matt Giuca]

A lot of places in the code manually compare the deadline to datetime.now(). There's already a method which does this, Project.has_deadline_passed(user), in database.py. All code should be changed to call this abstraction, because at some point (bug #492544), it will change to respect project extensions. (This is why it takes a user object).

[Matt Giuca (mgiuca)]

Fixed in r1510.