(TK-37) Increase default request buffer size and make request header size configurable

This PR does two things. First off, it bumps the default request buffer size as per ticket TK-37. In writing tests for this, however, I discovered that Jetty puts a limit on the size of the request header less than the new default value of the request buffer size, and if a header exceeds this limit, Jetty will return an HTTP 413 error regardless of whether or not the request buffer overflows. As a result, this PR has changed the default request size to be equal to the default request buffer size, and has also made it possible to configure the request size in a trapperkeeper configuration file.
Like was done for the corresponding proxy tests, I think it would be good to have the response body for the ring handler include the content of the big cookie and have the test validate that the cookie is present in the response.  Helps for validating that not only did Jetty not throw an error but it passed through the big header without truncating it.