Update for semantique

[luukvdmeer]

Just as the other affected components of the system (factbase and frontend) the manual needs a semantique branch in which we can update the documentation to correspond to semantique. This includes:

• Updating screenshots (either way some outdated screenshots need updating, e.g. the preview option is missing)
• Updating example videos and GIFS (which again often need updating anyways)
• Updating the building block descriptions
• Maybe refer somewhere to the existence of semantique as open source Python package