Restructure DB in preparation for follower/subscriber implementation

- Remove user.is{follower,subscriber}, replacing with tables follows and 
subscriptions
- Update vote_score_vw to reflect new structure
- Add db upgrade script

db/upgrade/v0.4-0.5.sql

@@ -0,0 +1,49 @@
+BEGIN;
+
+--UPDATE version SET minor = 5;
+
+CREATE OR REPLACE PROCEDURE update_vote_points(normaluser int, follower int, subscriber int)
+	LANGUAGE SQL
+	AS $$
+		UPDATE config SET normaluservotepoints = normaluser,
+			followervotepoints = follower, subscribervotepoints = subscriber;
+		CALL update_scores();
+	$$;
+
+CREATE TABLE follows (
+	userid integer,
+	PRIMARY KEY (userid)
+);
+
+CREATE TABLE subscriptions (
+	userid integer,
+	PRIMARY KEY (userid)
+);
+
+CREATE OR REPLACE VIEW vote_score_vw AS
+	WITH votepoints AS (SELECT normaluservotepoints, followervotepoints, subscribervotepoints FROM config)
+	SELECT requests.url AS url,
+		COUNT(votes.requesturl) AS count,
+		COALESCE(
+			SUM(CASE
+				WHEN follows.userid IS NULL AND subscriptions.userid IS NULL
+				THEN votepoints.normaluservotepoints
+				WHEN follows.userid IS NOT NULL AND subscriptions.userid IS NULL
+				THEN votepoints.followervotepoints
+				WHEN subscriptions.userid IS NOT NULL
+				THEN votepoints.subscribervotepoints
+			END), 0
+		) AS votescore
+		FROM requests
+		LEFT JOIN votes ON votes.requesturl = requests.url
+		LEFT JOIN users on votes.userid = users.userid
+		LEFT JOIN bans ON users.userid = bans.userid
+		LEFT JOIN follows ON users.userid = follows.userid
+		LEFT JOIN subscriptions ON users.userid = subscriptions.userid
+		CROSS JOIN votepoints
+		WHERE bans.userid IS NULL
+		GROUP BY url;
+
+ALTER TABLE users DROP COLUMN isfollower, DROP COLUMN issubscriber;
+
+COMMIT;