Remove zip archives (for now).

We had a long discussion at the TAG F2F and out of that came a dislike
of the zip format because it does not deal with MIME types and such.
Furthermore, http://esdiscuss.org/topic/generic-bundling#content-62
suggests this is not really worth it anyway. HTTP2 will save us.
Introduce filtered response concept
Define forbidden methods and author header names.
Add clarifying note.
Call out HSTS. https://www.w3.org/Bugs/Public/show_bug.cgi?id=22645
typo
Clarify internal response.
Fix typo from PR #3
Remove location from response for now. (Was only useful for redirects, which have to be atomic.)
Give up on ftp for now.
Cleanup links around caches
Clarify force preflight flag
Give response a url field.
minor cleanup