Code review comment for lp:~leonardr/lazr.restful/optional-compression

This branch fixes bug 450570; see there for details. Basically I create a configuration option that will stop lazr.restful from setting any hop-to-hop headers, and create a BaseWSGIConfiguration that sets that configuration value to false. This will prevent lazr.restful from doing things like setting the Transfer-Encoding header, which greatly displeases WSGI servers. (It doesn't displease the WSGI server I use in my tests, which is why this behavior is not tested directly, but it does displease real servers.)

It's a little unusual to change the web service configuration from a pagetest, but I thought root.txt was the best place for the new test since that's where existing compression behavior is tested.