Store a record of when data is pulled from TBA to (1) make use of ETag and reduce bandwidth, and (2) automatically sync data as-needed

[JL102]

This would allow #148 to be automatically handled by auto-pulling the list of teams from an event if, for example, the match schedule was updated more recently than when the team list was updated, and the team list has not been pulled in, for example, >6 hours. TBA supports ETag/If-None-Match headers (https://www.thebluealliance.com/apidocs) so if we store the etag and time of each of our TBA API calls, we'd be able to reduce the bandwidth requirements on TBA's servers from all of our syncing, and we'd be able to do some more "Let's automagically fix this data issue in the background" wizardry, without having to worry about the edge case where a recalculation/data-re-pull doesn't actually fix the issue, since we'd only re attempt that fix once in a while.