Manage physical machines with Fog.

Unlike virtual machines which rely on snapshots, Fog requires
the sandbox to be reboot; it then boots a small image pulled
down over the network and images itself via a Fog task.
Add basic configuration file to be used with Fog.
Added credentials to FOG conf
Changed reboot to RPC Shutdown; Added conf check for creds;
Rebased MITRECND-fog_dev onto feature/physical-sandboxes
Updating physical.py to work with rebase.
Minor fixes for physical machine manager
Fixes RPC reboot
Adding documentation for physical sandboxes.
Updating Physical Machine manager documentation
Merge pull request #383 from MITRECND/feature/physical-sandboxes

Physical Machine sandboxes