Introduce WebRequest::getProtocol()

The use of static server detection outside of its intended use case
(i.e. at the start of DefaultSettings.php), for example in r93258, was
an architectural error. Every other bit of information about the web
request in non-setup code comes from non-static methods of WebRequest,
which allows the request object to be meaningfully replaced or
subclassed. The situation became increasingly ridiculous as more
callers of WebRequest::detectProtocol() were introduced. Two of the
callers were calling it non-statically! I suppose they had the right
idea, in a way.

Using a non-static call allows caching, which is a nice additional
benefit.

WebRequest::detectProtocolAndStdPort() was introduced in r93258 as part of
the introduction of WebRequest::detectProtocol(). It was basically
useless. Grep indicates there was only one caller in core and WMF
deployed extensions, and it is patched here.

Change-Id: Ia0a61e98fbff7a46ceaeebcb02236e5eac3df0e1
Merge "Introduce WebRequest::getProtocol()"