update v13.0

The "Metropolis" update serie will include tons of new buildings and elements for your city,  with the goal to supply a complete and realistic city tileset  

Some more little additions before proceeding 

- Added a roof billboard with 3 new designs and 2 old from the road billboard
- Added the inner corners tiles of the second roof and more stuff to place on the plane roofs

See you and happy game-making! :)