Urban Simulator World

[NicoBartholomai]

Create a world in Gazebo for the urban challenge in iarrc.
Must have road-like streets with sharp terms, as well as a sign at each intersection with arrows pointing where to go.
It should also have a stoplight in the beginning that tells the car when to start.
This is important for testing the current Urban Challenge stack virtually and should try to mimic the actual competition as much as possible.