Add some documentation
Add some documentation

Working on #627

privacyidea/privacyidea,jh23453/privacyidea,privacyidea/privacyidea,privacyidea/privacyidea,jh23453/privacyidea,jh23453/privacyidea,jh23453/privacyidea,jh23453/privacyidea,wheldom01/privacyidea,privacyidea/privacyidea,wheldom01/privacyidea,wheldom01/privacyidea,wheldom01/privacyidea,privacyidea/privacyidea,privacyidea/privacyidea,wheldom01/privacyidea,wheldom01/privacyidea,jh23453/privacyidea