A single big image and block ids higher than 255

The first thing I added is an option to combine all tiles to a single big image. It is turned off by default. 
The second part is to allow high block ids which is impotant for some mods.

You can ignore the parts with the ColorExtractor and the changes to block-colors.txt. It's just something I messed around with and not that important. However you can add it if you like it. 
Pros: More ids and metadata. Cons: Colors changed a lot and some might not like the new look.

This is a sample render of a test world:
![big](https://f.cloud.github.com/assets/3699551/347877/dc7fa7c2-9f01-11e2-87fa-e7c00b520cb1.png)