Multiple bosh lite boxes

Made it possible to produce vagrant boxes which simplify running multiple bosh lites on one machine.

By using a packer variable file (such as 'second-instance-variables.json') a machien is built with a director on it designed to run with the vmnet2 address of 192.168.50.5 and cf machines in the 10.245.0.0/30 subnet.

This is precursory work for creating a second bosh-lite box that emulates an on-premises environment. 

See the story here: https://www.pivotaltracker.com/story/show/72087204
and the epic here: https://www.pivotaltracker.com/epic/show/1259432