Add script to publish all draft AAIB reports.

This script uses $stdout.flush and $stdout.sync = true liberally in
order to make sure the console output is legible and useful for whoever
in 2nd-line ends up running this script.

It uses the `republication` observers by accessing a new `republish`
method defined in the service repository.
Merge pull request #282 from alphagov/publish-aaib-reports

Add script to publish all draft AAIB reports.