Better handling of tournament start/end dates.

* defaulted start date to beginning of tourny if the late run date/time is null
* extracted constants for tourny start/end date/time
* added start_time property to tournament node in firebase
added new "total_bracket_points_for_round" property, which will save the front-end from needing to recalculate points totals per round
deleting unused files
removed logic that summed up column totals, since they're calculated by the backend now

need to do the same for row totals