Make the server type configurable

[Matt Jones]

For each section in the config.json, We should be able to specify a server mode:
fastcgi : For deployment with Lighttpd, Nginx, Apache2, Cherokee, et cetera
rootin_multi : The server process accepts requests and sends them to the app process to reply. The server rebuilds the app when the code changes.
rootin_single : One process that accepts requests and replies. No rebuilds.

The default will be:
development : rootin_multi
test : rootin_multi
production : fastcgi