Factor out db_backup tools for fabric and cron

The logic for running remote backups is not located in a db_backup
file that can be used as a script for a cronjob. The fabric file
imports these functions to remain DRY.

Added an __init__.py file so that the fabfile could find the db_backup
module
Add cronjob for backups

Partially fixes #193 on github. Partially because we are in the
process of merging out build tools to work on both dev and production
servers. In the meantime, someone needs to remember to run these
commands piecemeal on the production site to get the cronjob working.