Code to run svscan on startup on mac and linux

specifically we install the startup scripts (rendered from the erbs)

Then, on a mac, we make sure that the appropriate paths are extant for
launchctl. If not, we examine the current paths, and install the new
paths, keeping the old paths sane.

we also write our new paths to /etc/launchd.conf so that they persist
after reboot.
file used to create the new launchd.conf on a mac
svscan initscript for linux (UNTESTED as of now)
launchd script for svscan for mac