Xporter for JIRA entry should only be visible according to permissions

The Xporter for JIRA entry in the Export menu should only be visible to users that have the permission to use it.

We want to introduce the Add-on for a pilot group, but every user is able to see the entry. If a user that is not part of the pilot group tries to use the add-on the giant error message appears.

This must be applied to the Issue detauil screen.