Add 'cash_in_txs' migration

This migration adds a new column to the 'cash_in_txs' table to
accommodate the new paper wallet feature for compliance.

migrations/1552064796155-tx-paper-wallet.js

@@ -0,0 +1,15 @@
+'use strict'
+
+const db = require('./db')
+
+exports.up = function (next) {
+  var sql = [
+    'ALTER TABLE cash_in_txs ADD COLUMN is_paper_wallet boolean null DEFAULT false',
+  ]
+
+  db.multi(sql, next)
+}
+
+exports.down = function (next) {
+  next()
+}