Added CampaignMap and MapLevel classes to the game code.

CampaignMap generates the map every level and passes it down
to the MapLevel class to render and set up player interaction.

Both classes are still a work in progress.
Added a tutorial map to the game. The map is loaded from an XML file and
will be static, except for road denominations.
Game now displays fraction values near each road segment.
The car is back and can drive across roads one at a time when the
player clicks on a valid road.
Vehicle now moves to destinations when player clicks on it.
Multi-road selection/de-selection and driving now available.
Fixed road selection/de-selection bugs and added visual cue when
selecting road more than once.
Clicking is disabled while the vehicle is in motion.
Started putting together the tutorial UI.
Car now grows bigger when moused over.
Removed road highlight when hovering over road.
Hovering over structures enlarges them and shows their labels.
Reverted car enlarging code.
Scrolling the game now offsets the interactive areas correctly.