Refactored player coordinate/velocity handling into separate structs
Distances are now measured in cube lenghts (instead of meters)

This will allow us to determine the effective cube size through configuration -- if you scale up all values by 2, the visible cube size is halved.
First stab at player movement

At the moment, walls are "sticky" and player size isn't taken into account at all.
Extracted GameData into separate project to make IntelliSense work in the XAML editor