add: Added .cleanupguilddata command which will delete all guildconfigs, xp stats and other data related to any guild the bot is no longer in. This is a highly destructive and irreversible command.

dev: Added cascade deletes to any tables which have guildconfigs FK, as well as to some other missing places

src/NadekoBot/Db/Models/xp/XpSettings.cs

@@ -51,6 +51,8 @@ public class XpCurrencyReward : DbEntity
 
 public class ExcludedItem : DbEntity
 {
+    public XpSettings XpSettings { get; set; }
+
     public ulong ItemId { get; set; }
     public ExcludedItemType ItemType { get; set; }