cleaner rel. we only need to start the applications.
make couch_httpd a full couch application

With this change, the HTTP API is now handled by its own erlang
application and supervision. It also improved the way you can reload the
configuration and the modules. Now upgrading a listener or its
configuration is first removing it from the supervsion then start the
new process with the new configuration. This behaviour is similar to the
one you have in nginx.