Separate Bediende page to show details

[heynist]

We definitely need a separate page for showing the details about a Bediende.
Linking to this page, can be done from any place where a Bediende is shown in an overview.

On the page we should see the contractual situation, and the planning situation for the Bediende.
This includes personal details, the relevant Contract(s), the Akkoorden and Bestelbonnen.

Ideally we should see only the actual and future relevant information in 1 tab, and the historical information in a separate tab. That way, we have an immediate relevant overview of the Bediende's situation.

Think of this page as a kind of dashboard of a Bediende.

This could later evolve into a page which the Bediende himself would be granted access to, in order to enable self-service.

For now, this page should only be accessible to the Administrator.