Pulled the generic <T> and Value property out of the HexMapItemBase and moved it into HexMapItem since it didn't have anything to do w/ hexes per se and prevented me from making extension methods on all derived classes.

Added a VerticeDirections list so it's easy to find a vertex by direction or vice versa

Added the HexWpf project to provide WPF-specific extension methods to represent things like coordinates as Point structs instead of generic Tuples, and to translate Cartesian coordinates to screen coordinates.