Merge pull request #258 from gaethofs/master

Contraints in schedular voor admin
sorting op homepage
Merge pull request #259 from svdvonde/master

Issue 257 (gesorteerde programma's/trajecten op homepage) opgelost
Merge branch 'master' of https://github.com/CalZoneVUB/CalZone

# By Sam
# Via Christophe Gaethofs (1) and others
* 'master' of https://github.com/CalZoneVUB/CalZone:
  sorting op homepage