DownloadController to log downloads DCDEV-65
This adds the DownloadController providing an endpoint to record the download and redirect to the download url that is passed as a query param.
It does not log downloads from CEH staff listed in the metrics.users.excluded property.
It is designed to work when a MetricsService does not exist, such as when the profile is not 'eidc'.
The freemarker template responsible for creating the download link (_distribution_dataset.ftlh) has been updated to use this controller.
Closes DCDEV-65