Add django-npm to manage node packages

Installs https://github.com/kevin1024/django-npm

• adds npm static finder for local development
• collects node module via collectstatic, can be customized via settings NPM_FILE_PATTERNS
• path to static needs to be according to node module folder structure in templates

This is marked WIP because there are other packages with similar outcomes, they should be discussed:

• https://github.com/owais/django-webpack-loader
• https://djangopackages.org/grids/g/static-builders/
• https://django-pipeline.readthedocs.io/en/latest/usage.html