Added chunk, world and block interfaces

src/org/bukkit/World.java

@@ -0,0 +1,18 @@
+
+package org.bukkit;
+
+/**
+ * Represents a world.
+ *
+ * Currently there is only one world in the default Minecraft spec, but this
+ * may change with the addition of a functional Nether world
+ */
+public interface World {
+    public Block getBlockAt(int x, int y, int z);
+
+    public Chunk getChunkAt(int x, int z);
+
+    public Chunk getChunkAt(Block block);
+
+    public boolean isChunkLoaded();
+}