Add noproxy configuration

When fetching, check if the url requested must use a proxy (if present) or not.
This allows package installation from lan without having to change/disable the proxy parameter each time.

"noproxy" is a string containing hostnames. When fetching a package from one of these hostnames, the specifed proxy won't be used. 
So, this add a way to specify a list of hostnames that will not ever go through a proxy.

Note: Most relevant addition can be found in lib/utils/fetch.js.