Allow to get server URL, port, name, scheme

Summary:
To determine the URL of a server, three components are needed:
the scheme (http? https?), the name and the port.

Generally, ports won't be the in URL, as they are the default
80 or 443 ports.

Advanced network configurations

Furthermore, in back-end/front-end topologies, To determine
if we're in HTTPS requires to examine several headers.

If there is now a standard, RFC 7239 section 4, a lot of load balancers,
caches or web servers use proprietary or former de facto headers.

Deprecation

The new Request::getServerURL method supersedes get_server_url
from Keruald/Xen sites like Azhàr or Zed.

Test Plan: Unit tests provided

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1636