Oauth school selector: Allow to chose 'no school' in school selector in order to allow to retreive old data

Oauth login: Throw error instead of silently ignoring school information not being configurerd on teacher login via PMS

Enable configuration options to be passed through to certain (later possibly all) templates directly

Template jwinf: Optionally require field sex in profile, optionally allow 'no answer', 'diverse' or 'other', respectively, configurable via config file

Ask users on OAuth login to fill in their user data (especially grade). Fixes #96. Also some formatting