Fixed player sprite not respecting Y axis positioning on camera.
Hugely expanded map

Huge map system that divides the world into quadrants.  Map resources
are not loaded until the player is nearby.

Things to work on:
-- Wrapping in X and Y
-- Normalize the islands so that they "snap" to the tile grid
-- Add collision to the islands
-- Draw sprites appropriately if they're behind some land
-- Implement minimap
Visual glitch fixes, added items

Added collectable items. These can be added to an island's local map by
simply adding the item using TileMap.addItem(), and the local map
coordinates.  Specific islands can be added anywhere on the global map
using Map.addIsland()

Items collected currently do not influence the player state, but they
stay gone if collected.  They load and unload just as their parent
island maps do.
merge upstream/map
Fix bullet after merging map