Make it clear where we are using Mockups

[kohlhase]

Currently, https://beta.mathhub.info/applications/glossary is a Mockup, i.e. the Frontend component exists, but there is no backend.

It would be great, if we could make this transparent (and do so generally for all mockups we currently employ). E.g. by adding (Mockup) to the page title and the sentence

This application/page is a frontend mockup without a backend for the moment. 
We use it for testing the user interface on static content; please feel free to give us feedback. 
You are not seeing actual MathHub content, but a manually written and aggregated example.

below it.
If we could do that generally, that would make the state much clearer. I am sure we will use mockups in the future to do new features, so this will pay off.