Daemon

If you call ./run-as-daemon OctoPrint runs as a daemon. The default ./run is left unchanged.

Changes in server.py primarily to prevent early starting of threads before forking into a daemon, this was where most issues were.

Would be nice to remove the need for the global printer, gcodeManager and flask app.

./run-as-daemon is currently a python script but could be incorporated into run in some cunning way but this way less likelihood of breaking existing behaviour.