Fix bugs in importing XML feed.
Local changes for blue network
We use proper certificate validation instead
Ignore submissions that are before the starttime, rather than erroring out.

The feed may include some old submissions.
Also track total number of result differences with external ccs
Add debugging, change error to warning, fix api endpoint.
Fix importing of external ccs results
Fix replacing/appending std. answers after editing.
Chop off second precision of freeze and endtime in contest.yaml.

Our contest relative times do not support second precision and we
don't see it as a useful thing to implement, so just chop it off
on import to prevent data validation problems later.