iCAT time elapsed depends on accurate time set on browser

[ghamerly]

Events displayed in iCAT display how long since the event happened, e.g. "5 minutes ago". The calculation for this elapsed time is done in Javascript on the browser, and depends on doing a subtraction between current time on the browser and the time of the event. Thus, if the browser's computer clock is wrong, the elapsed time will be wrong. It also currently has a hack which requires the Javascript to know the timezone of the contest (which is also set in the config.yaml, but JS does not pull from there).

We need to rework the javascript elapsed time calculations so that:

1. it does not rely on the browser's time being correct,
2. it does not need to know the timezone of the contest, if possible, and
3. if it does need to know the timezone of the contest, it pulls it from the config file rather than hardcoding it.

[sjoqvist]

I created #34 to at least solve a part of this. This ticket might still need to be revisited afterwards.