iptables.dump, null safety for common args

Adds an iptables.dump method to parse out iptables-save. I might suggest moving table and chain out of the various functions options argument in order to make this easier to dogfood back into the utility methods.
Defensive technique vs people trying to use well crafted .hasOwnProperty to change how things act. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty#Example.3A_hasOwnProperty_as_a_property . Unlikely, but habit after years of JS.