HACKED TOGETHER time limit for DB class midterm

[jbau]

Note this is to edx-west/rc, not master:

@jaericson
Please review thoroughly and test on your dev environment thoroughly. If I don't get a thumbs up from you before say noonish tomorrow, then I won't release.

@nparlante can you be the second reviewer on this (also before noon tomorrow)? I'll explain in email.

[jbau]

This is a hacked capa timed exam. It only works within DB class parameters (i.e. 1 submission allowed). Timer starts when the exam is rendered to the student ("get_problem_html()")

[jaericson]

I just tested it, and it looks great to me! Thank you so much for doing all of this under an impossible timeframe! Not sure what the "tests failed" below means.

The only item I'd change, since we're patching this now exclusively for the midterm (and later final) exams in the DB class, is the wording in the problem.html file to this:

At (time), you started this exam.
By (time), you must manually click the "Final Submit" button at the bottom of the page!

Here's what I tested:

• leaving the problem doesn't reset the starting or ending time
• one can successfully submit before the timer has elapsed, up to and including the 1-minute grace period
• one is told that the problem state has changed and must reload the page if they click the submit button after the 1-minute grade period
• progress reported correctly when able to submit; progress is 0 when trying to submit after the deadline
• when the exam is due before the start time plus allowed_minutes, the exam due time is displayed, not the start time plus allowed_minutes

Thanks so much, Jason!