Bower not used anymore

The Helfertool repository now (again) contains all JS and CSS dependencies. This means that npm and bower are no dependency anymore, this should make deployment easier and save around 50MB of disk space.

This means that the node_modules and helfertool/components directories can be removed. It is recommended to run python manage.py collectstatic --clear to remove the old files from the static files directory that is served by the web server.