NX-493: Integrated service with proxy and hosted repo
NX-611: NPM Proxy repository
NX-498: NPM Hosted repository
NX-490: Registry root metadata is not cached (WIP)
NX-491: Use of GSON dropped

Initial implementation of proxy and hosted repositories
using the new metadata service. Dropping many of the (now)
unused stuff, also, GSon proves to be not needed anymore.