Better handling of the biome tinting images.

If they're not found with _find_file, then look in the EXTRACTEDBIOME
folder in the worlddir.

world.py

@@ -26,6 +26,7 @@ import numpy
 
 import chunk
 import nbt
+import textures
 
 """
 This module has routines related to generating all the chunks for a world
@@ -102,6 +103,9 @@ class WorldRenderer(object):
         self.cachedir = cachedir
         self.useBiomeData = useBiomeData
 
+        if self.useBiomeData:
+            textures.prepareBiomeData(worlddir)
+
         self.chunklist = chunklist
 
         #  stores Points Of Interest to be mapped with markers