vehicle cargo volume display

Moved top speed to display alongside safe speed in a Safe/Top format.
Added used/total cargo volume display.

![screenshot - 04122014 - 04 04 49 pm](https://cloud.githubusercontent.com/assets/4959959/2688011/cc951dce-c27d-11e3-8146-93ed940f24c2.png)


Truck in screenshot has a bottle of water in the box between the seats and a pipe in the passenger set.