Save default content with batch API

We currently save some default content as part of the Commons installer without using the batch API. This can lead to long execution times and memory usage within a single request, and even fatal errors (eg, #1035486: Fatal error: Maximum execution time of 60 seconds exceeded in C:\wamp\www\commons\includes\file.inc on line 937).

A better way of saving this content would be to use the Batch API. Commerce Kickstart, for example, uses default content and users as a csv and saves the content with the Migrate module.