Show general messages

[daniel-lerch]

Some representations or canceled hours are not shown for each class but in a section called Nachrichten zum Tag. Especially the row Unterrichtsfrei only appears in some weeks but is very important for all pupils. This information has to shown somehow to the user.

[jrheiner]

Added in bf7b300
App now shows the Unterrichtsfrei message. If there is more information that affects all students feel free to notify me.