Batch auto retire

When a batch is 'retired', the DB records of its jobs and job instances are deleted, and its input and output files are deleted. Only the batch record remains.

To avoid running out of disk space, batches must eventually be retired. This can be done as follows.

First, run this periodic task:

<task>
    <cmd>run_in_ops ./submit_retire.php</cmd>
    <period>1 days</period>
</task>

• If a batch has been completed or aborted at least 7 days ago, the submitter is sent an email asking them to retire it.
• If a batch has been aborted for more than 14 days, it's retired.
• If a batch has been completed at least 30 days, it's retired.