Add database management API calls and update crons

[howard-e]

Partially address #759 in making it easier to get a database dump from production and restoring it in staging or sandbox.

This PR adds API functions:

• Dumping postgres database
• Restoring postgres database
• Cleaning up the database dumps directory so it doesn't grow too large (defaulted to max of 28 days)

This PR adds the following cron jobs:

• Dumping postgres database every day at 00:00
• Cleaning up the dumps directory if necessary every day at 00:05