Make inactive dataset feature tabs greyed out

[JaseMK]

Show inactive features in a different colour and unclickable.

Eg, the SPARQL or FILES tab for a dataset that's not yet activated.

[JaseMK]

Rather than grey-out for unavailable tabs, all tabs should be selectable. If navigating to a tab that the user doesn't have access to, the page should still load with an appropriate message informing them that they do not have the required permissions.