Add difficulty selection menu
Add stub City and CityView

CityView will be the screen handling the cityscape
'City' will be the class storing the current state of the city (A core
part of the game state)
Load city tile IDs
Citymap is 10 high, not 100
Add trivial static city renderer
Initialse pck pixels to transparent

If a pck file does not define a pixel, it should be trasparent, so init
them to (0,0,0,0).

This stops undefined data being in the unset pixels, causing rendering
artifacts on some platforms/runs
Add new citymap files to msvc project

This is untested - hope it works!