Renamed: LivingNeighborsOf*CellCountedHandler -> DetermineNextStateOf*Cell

I decided that it is more descriptive to state the purpose of "handlers"
as a verb, since they are generally fairly procedural, than to simple
state *what* it is handling. This follows my naming conventions in the
C# version of this project, which I now favor.
Renamed: location -> position
Renamed: CartesianPosition -> Position

Working in a grid is different than working in a coordinate plane...
Promoted Position from a struct to a class

Gave it a source file and worked on its encapsulation. Am going to
determine it into its own legitimate object.
Playing around with some fluentish Position stuff
Added some specs for Position
Added another unit test to PositionTests