clone: save app config

clone also clones the tags, labels and icon. this is not done for
restore or import since it's not clear if this is a good idea or not.
for example, if user had some custom tags and label set and then restores
to some old backup, is it expected to reset the labels and tags?

src/appdb.js

@@ -33,7 +33,7 @@ exports = module.exports = {
     _clear: clear
 };
 
-var assert = require('assert'),
+const assert = require('assert'),
     async = require('async'),
     BoxError = require('./boxerror.js'),
     database = require('./database.js'),