Add PostgreSQL replication script

Dumps stagecraft and imports it into dev vm. This requires that no users
are connected to the dev vm PostgreSQL, if there are then it will blow
up.
Stop collectd while restoring

We need to remove collectd's connection to the stagecraft db so the
restore can happen.
squash-me reset password
fixup: drop db before restoring
Tidy up replicate script

Replaced a reference to mongo and backdrop, which is where this script
is copied from.

Enabled removal of the dump as it won't be needed after completion.
Merge pull request #280 from alphagov/feature/db-replication

Feature/db replication