Support for HTTP Link Headers

[sgammon]

Support the expression of related static assets as HTTP Link headers. According to spec, sending such a header is equivalent to specifying a <link rel=''> tag in the HTML inline.

Currently, Chrome doesn't handle this properly and it seems only newer versions of Firefox and Opera would benefit, making this a good candidate for implementation via Content Filters (#12). Support for it now would mean instant use later when support improves (as it seems it will).

Relevant specifications:
http://www.w3.org/wiki/LinkHeader
http://tools.ietf.org/html/rfc5988

Browser notes:
http://www.chromium.org/spdy/link-headers-and-server-hint/link-rel-subresource
https://developer.mozilla.org/en-US/docs/Link_prefetching_FAQ
http://css-tricks.com/using-css-without-html/
http://meyerweb.com/eric/thoughts/2009/01/22/using-http-headers-to-serve-styles/
https://support.google.com/webmasters/answer/139394?hl=en

Note about rel="canonical" (should have its own issue someday): http://googlewebmastercentral.blogspot.com/2011/06/supporting-relcanonical-http-headers.html

[sgammon]

Could be cool to expose an interface to Services for this. Would be easy with Service Middleware (#21)