cron jobs for db backup and reindexing

[willkg]

I threw these together and tossed them in the pyvideo-deploy repo because I needed them for pyvideo and wasn't sure if they were general things people would want to do with richard.

https://github.com/pyvideo/pyvideo-deploy/blob/master/roles/pyvideo/tasks/main.yml

Two things:

1. should these be in richard-ansible instead?
2. should they be enabled/disabled via a setting or maybe put in a separate role so people who don't want them don't need to have them running?

[willkg]

@codersquid pointed out that the db backup cronjob should be part of the postgres role. We could make the reindexing one part of the richard role.