Extend HttpPropertyType enumeration to support two additional value types with the getProp method:
1. A named HTTP header
2. An unnamed socket endpoint address

Some users of the secure context make decisions based upon the contents of the "x-forwarded-for" header and the socket address. The secure user peer, which is currently available in security manager plugins, is derived from these values but is insufficient.

A security manager which restricts access based on the originating IP address may choose to bypass this restriction for requests originating on the local host. A derived peer that is a local host address is not proof that the request originated locally - the local host address could be a result of a spoofed header. The socket address alone is also not proof, as the request could be forwarded from a proxy running on the local host. A socket endpoint that is a local host combined with the absence of a forwarding header provides greater confidence of local origination.