WIP: Frontend demo

DO NOT MERGE

This branch relies on request !127 (merged) Changes for the demo:

• the demo course (name configurable) is shown first over otherwise equal courses
• roles can be changed in the frontend under /roles
• when the demo runs in dev mode, AKA localhost, the following netids have a fixed role:
  • mpigmans: student
  • mvandeursen: manager
  • ghabbenjansen: verifier
  • rkeulemans: scheduler