Features/webserver bugfixes

I made a large number of very opinionated changes to `JettyServer`. It's up to you to pick which ones you want. You can use [`git cherry-pick`](http://git-scm.com/docs/git-cherry-pick) to accept some commits, but not all; or you can just merge the whole thing. Up to you.

Once this pull request is cleared, I think I'll be okay with merging `webserver` to `master`.