added shadowcasting FOV code(unimplemented yet) from RogueBasin
adding strings file to git
implemented and cleaned up shadowcasting FOV code from Python example on RogueBasin(http://www.roguebasin.com/index.php?title=PythonShadowcastingImplementation)
refactored classes into separate files for better organization, split mathematical functions and algorithms out to a separate library for easier optimization later.