Modifies mcb package and mcbconv to track additional world data.
In this case, it is the outer bounds of chunks in a world.
These come in the form of 4 integers: chunkMinX, chunkMinZ,
chunkMaxX and chunkMaxZ, which are stored as part of the
World structure and persisted to world.js.
Applies some bug fixes and amendments to mcb package.
Implements part of mcmapgen. World is rendered to an image at maximum
zoom level (1 pixel/block).
From this, map tiles will be generated, as well as all lower zoom levels.