Redesign CoC module

[Pythonic-Rainbow]

Instead of ClanUtil, use ClanDelta and extension methods

e.g. Coc.GetMember -> Clan.GetMember (by using extension methods)
comparing 2 clan instances in order to see who left clan/donated stuff: Methods/Properies in ClanDelta

During Coc module init, fetch clan info once and ClanDelta clanDelta = new(clan);
For each poll, clanDelta.compare(newClan). and then compute stuff like clanDelta.membersLeft

[Pythonic-Rainbow]

After reviewing the TODOs, if really giveup SQLite Trigger approach:

In Db.cs, Create events and implement a callback for each event
In DbObj impl classes, call those events

e.g.
Override Account.Insert {
Db.EventMainInsert();
}

---

Or simply just
Override Account.insert {
Main main = new();
main.Insert()
}