Use bootstrap buttons instead of input tag.

See merge request Teckids/BiscuIT/BiscuIT-ng!52

This is wrong from a Python point of view, but the default in the
Django Template Language.

Currently translated at 100.0% (108 of 108 strings)

Translation: BiscuIT School Information System/BiscuIT-ng
Translate-URL: https://translate.edugit.org/projects/biscuit-sis/biscuit-ng/de/

Use existing template. Closes #92.

Closes #92

See merge request Teckids/BiscuIT/BiscuIT-ng!51

Add way to edit information about school and school term. Closes #19.

Closes #19

See merge request Teckids/BiscuIT/BiscuIT-ng!50