Add a bundle to do postgresql maintenance (vacuumdb)

Regarding https://cfengine.com/dev/issues/5311

* agent bundle to stop cf-hub and cf-consumer before running vacuumdb
* pre-defined running once a week on Sunday 2am
* if vacuumdb is still running, we don't restart cf-hub and cf-consumer in update.cf
* haven't touched anything in body hub control{} yet

@awsiv, @jeffali what do you think?