Light control

[alexdarling]

Refactoring code in the LightControl object so that future development is easier:

• Simplifies LightControl's state-switching and state-tracking
• Stores the most recently overwritten state (other than all-red)
• Plans out lights using a queue based on the most recently overwritten state

Also, adds hasCar() to Lanes.

[alexdarling]

There will be merge issues due to work in the car-visuals branch. We are going to merge that into master first and then merge this in.