Support for ServerID to support nexus raw proxy repositories with authentication

It would be nice to support or use std. maven features for downloading http based content so basic features like authentication via server config in settings.xml would be supported.

The clients do not have a direct internet connection. I like to use the nexus raw proxy repo to cache the data. Due the lack of support for http authentication i've to give anonymous access for the nexus repository to use nexus as cache for the cve data. I do not like to give anon access to that repo.