Rated educational

[victorsenam]

We need to inform rating changes for rated educational rounds. Two main solutions were proposed

• Checking whether a contest is rated with a regex on contest name.
• Checking for rating changes for some time after the contest's end and, if there were none, check again the next day.

I prefer the second because cf might stop saying 'rated' on educational rounds if this becomes standard.

[victorsenam]

I'll insert some logging on the current rating changes checking procedure so that we can easily create tests for this feature later.