Add passenger sysvinit

Adds a sysvinit script for passenger based apps.

Stops the daemon by adding a tmp/stop.txt file [1],
which requires a httpd directive to return 503 if the
file exists.

[1] http://blog.flowdock.com/2009/03/11/stopping-your-rails-application-with-phusion-passenger/
Fix down.default.html asset paths
Make down.default.html generic