(Tasklist): Make tasklists global.

data/migration/v0-v1/migration.sql

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+ALTER TABLE tasklist DROP COLUMN guildid;
+CREATE INDEX tasklist_users ON tasklist (userid);
+
+ALTER TABLE tasklist_reward_history DROP COLUMN guildid;
+CREATE INDEX tasklist_reward_history_users ON tasklist_reward_history (userid, reward_time);
+
+
+INSERT INTO VersionHistory (version, author) VALUES (1, 'Migration v0-v1');

data/migration/v0-v1/notes.md

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+The purpose of this migration is to remove the guild dependency on tasklist tasks, so that a user's tasklist is available across all guilds.