Store invite in database and sync power on startup

db/migrations/0012-add-member-power.sql

@@ -0,0 +1,14 @@
+BEGIN TRANSACTION;
+
+-- the power we want them to have
+CREATE TABLE IF NOT EXISTS member_power (
+	mxid			TEXT NOT NULL,
+	room_id		TEXT NOT NULL,
+	power_level	INTEGER NOT NULL,
+	PRIMARY KEY(mxid, room_id)
+) WITHOUT ROWID;
+
+-- the power they have
+ALTER TABLE member_cache ADD COLUMN power_level INTEGER NOT NULL DEFAULT 0;
+
+COMMIT;