Physical Machine sandboxes

This is a refresh of the code originally submitted in Pull Request #75 and now in the [MITRECND-fog_dev branch](https://github.com/cuckoobox/cuckoo/tree/MITRECND-fog_dev). It has been updated to work with the most recent version of Cuckoo, generalized from just Fog to work with any solution which can automatically reimage physical machines, and [documented](https://github.com/MITRECND/cuckoo/blob/677bbab91f532f47998de1ae0a0bf08c3ff21302/docs/book/src/usage/physical.rst). This code has been being used since the original pull request and has proven generally stable, though any additional testing would be appreciated!

Thanks, to @Locker537 , @kholbrook1303, and @robertsjw for writing and testing this code.