cloudron-setup: move backupConfig default as migration script

if in autoprovision, then the backupConfig ends up being overwritten
after a restore.

migrations/20171205124434-settings-default-backupConfig.js

@@ -0,0 +1,23 @@
+'use strict';
+
+exports.up = function(db, callback) {
+    var backupConfig = {
+        "provider": "filesystem",
+        "backupFolder": "/var/backups",
+        "format": "tgz",
+        "retentionSecs": 172800
+    };
+
+    db.runSql('INSERT settings (name, value) VALUES(?, ?)', [ 'backup_config', JSON.stringify(backupConfig) ], function (error) {
+        if (!error || error.code === 'ER_DUP_ENTRY') return callback(); // dup entry is OK for existing cloudrons
+
+        callback(error);
+    });
+};
+
+exports.down = function(db, callback) {
+    db.runSql('DELETE FROM settings WHERE name=?', ['backup_config'], function (error) {
+        if (error) console.error(error);
+        callback(error);
+    });
+};