Do not proxy API requests

Remove proxy from node setup, because it makes things unnecessarily
complex.

This was introduced to avoid same-origin-policy issues, however they
should be fixed on the API server side by setting appropriate CORS
headers (basicall accept all).

This has already been done for the django services in the following PR:

    https://github.com/policycompass/policycompass-services/pull/2

It might also need to be done in FCM and elastic search.