Bug 33261: Format dates in subscription_issues table

Bug 33261: Format dates in subscription_issues table

To test:
* Add a subscription
* Receive some issues
* Go to the subscription detail page, issues tab
* Verify the dates there display as YYYY-MM-DD
* Change DateFormat system preference setting, nothing changes.
* Apply patch
* Date should now be formatted in the way specified in the DateFormat system preference

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>