Added a more road models, updated make to gazebo 2.1, added correct collision
 data to the road models and attemped to do the same for the chassis. Tried
to build a new world for testing (crossroads2.world) but it doesn't save the
car models properly. To do: Find out why the road models have huge select boxes
 why the chassis has the position changed by default, why there are some
artifacts in the road models.