Enable compression for JS, CSS, JSON and XML responses

Some static .js and .css files in particular and dynamic JSON and XML responses can be quite large, and would benefit from being compressed to reduce load times and bandwidth usage.

There are several possible approaches:

1. Frontend httpd servers like Apache httpd can compress on-the-fly with mod_deflate for specific content-types:

http://httpd.apache.org/docs/current/mod/mod_deflate.html

Sample configuration in httpd.conf:

# mod_deflate (compress output for browsers that support it)
AddOutputFilterByType DEFLATE text/html text/plain text/xml text/css application/x-javascript text/javascript text/x-js application/json application/xml application/javascript

2. We could set a gzip compression filter in jetty:

http://www.eclipse.org/jetty/documentation/current/gzip-filter.html