Add user agent to access log output

Currently the access log includes a timestamp, user name, originating IP address, HTTP method, and the request target (which could be a URL, action, screen). We often need to know how the user actually made the request, which can be determined (for the most part) from the User-Agent header of the request, but can only do this by cross-referencing the request with the front-end proxy.

Streamline the AccessLogger log methods and add the User-Agent header where possible.