Refactoring:
Moved basic grid creation and related functions to world class
Created World object before pyglet begins running application, to which draw calls can be made
isLand and isWater flags for hexagons are now known just as land and water, because isLand looked like the world Island
Removed redundant functions countNeighbours and countHexesInGrid which were originally only created for diagnostic reasons
Renamed floodfillLandRegions to createLandRegions when the function became a member of the World class
Renamed screenClipGridHexagons to clipGridHexagonsToWorldDimensions to be more fitting