+ http: New Raw-Request-URI header that can be added by the server if configured to do so.
+ can: Support access to the undecoded request target URL.

Access is a via a new Raw-Request-URI header, and only if the spray.can.server.raw-request-uri-header setting is set to on. It defaults to off.
= can: Improve description of the raw-request-uri-header setting.
+ util: Publish the Charset corresponding to US-ASCII.

This allows code avoid repeated lookups, similar to the existing Charset for UTF-8.
= can: Fix accidental JDK7 dependency.
Merge branch 'asnare-issue/raw-url-access-mkii'