Add support for Cumulus Networks Linux

This adds support Cumulus Networks Linux (http://www.cumulusnetworks.com) which is a derivative of Debian. The PR includes the command support as well as a change to the Debian OS detect process: Cumulus Networks has the literal string 

```DISTRIB_ID="Cumulus Networks"```

in /etc/lsb-release which obviously needs slightly more cleaning up (removing the quotes & space in the middle)