Add script to fix stale cached values

sql/branch.py

@@ -0,0 +1,16 @@
+from gratipay import wireup
+
+db = wireup.db(wireup.env())
+
+participants = db.all("""
+    SELECT p.*::participants
+      FROM participants p
+      JOIN payment_instructions pi ON pi.participant = p.username -- Only include those with tips
+""")
+total = len(participants)
+counter = 0
+
+for p in participants:
+    print("Participant %s/%s" % (counter, total))
+    p.update_giving_and_teams()
+    counter += 1