Sort OPRs & Event/Team @ Event info tweaks.

I started this branch from the team_at_event_summary branch, so this should probably be merged with that before being merged into the master.

- Event stats are now properly sorted by OPRs.
- Changed team links in event rankings & stats to Team @ Event.
- Fixed possible NPE in PopulateEventInfo (as noted in #83)
 - Added basic case in MatchHelper & PopulateTeamAtEvent where match information is available but no alliance data (for past events)
- Extra code cleanup/documentation.

I was thinking about updating the "no alliance data" case to be something like "No alliance data is available, but they were..." but I feel there's a simpler way of doing that without just doubling the enums (not to mention "NO_ALLIANCE_DATA_ELIMINATED_IN_QUARTERS" is a bit long to me).