Adding "Aktive" and "Ehemalige" team page

Solves https://gitlab.com/foodsharing-dev/issues0/issues/205

Since it's my first commit to the foodsharing website, please let me know if you have any recommendations, and be patient with me code-wise : D

To-Dos

• Create "Ehemalige" page
• Create content boxes on foodsharing.de server
• Add "Aktive" underneath "Vorstand"
• Open possibility to see user-pages with rolle < 3 that are in Ehemalige or Aktive
• Add Link "Ehemalige" to "Ueber Uns"