Remove unnecessary function
Add braunschweig reader

Based on https://github.com/okfde/odm-datenerfassung/blob/master/readdatacatalogs/braunschweig-geoportal.braunschweig.de.py
Add diepholz reader

Based on okfde/odm-datenerfassung/readdatacatalogs/diepholz-gdi.diepholz.de.py
Add utility functions
mend