HTTP Server should respect Connection: Close and/or Keep Alives

[panesofglass]

We currently don't do any connection management, but HTTP specifies how this should work. We should pay attention to Keep Alive and Connection headers and take the appropriate action. The current implementation doesn't make this very easy, so the new compositional architecture could greatly help facilitate this request.

[hammett]

FYI I'm trying to make this work out of pure need and it's quite involved.

[panesofglass]

You should be able to find something like this in the following commits:

1. commit 5193644
2. commit 69d0c8d
3. commit 9626cd6
4. commit ed3cbda

Note: these are in our Pipelets branch and not 100% ready. That said, it's much better performing than master.