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!
Don't re-align pck images to the first top/left pixel defined

For tiles that do not use the first column/rows (IE most of them) we
re-aligned the entire image to the first row/column actually used (IE
non-transparent). This caused the tile to be mis-aligned on the
cityscape, so no longer do that

This makes the stored tiles slightly larger, padded with more
transparent pixels, but memory is cheap these days...