Feature/1253 create a script to configure auto launch of server on startup on mac

Hi @aronasorman - This is for #1253 - Create a script to configure auto-launch of server on startup, on mac - it uses `launchd` and `launchctl` on OSX.

I still have an outstanding question on the issue above whether we launch the KA Lite server:
1. on user login
2. on startup

These changes are based on option 1 - on user login.
This file's name is `setup_linux.sh`. Might be good to rename it to `setup_unix.sh`.