F indigo base

Adds support for an indigo (trusty) base image. Also basic plumbing to build multi machines from the same vagrantfile to make managing base images easier.

Note this fails as there is [no ros-indigo-desktop-full](http://answers.ros.org/question/155241/installing-ros-indigo-on-ubuntu-1404-lts-trusty-apt-get-unable-to-locate-ros-indigo-desktop-full/) for trusty yet. Looks like the [release is targetted for april](http://wiki.ros.org/indigo/Planning).