Added a Game class to dictate the game's lifecycle

|SOURCE|
[Common/DataTypes]
* Added basic data types to allow for cross-platform and cross-wordsize
  building
[Common/Game]
* This governs the lifecycle of the game, including rendering and updating the
  game
[Common/Main]
* An instance of the LD::Game class is instantiated and used to abstract the
  platform details of initialising and running the game