Add greenvars script and sprites, works for previewing on somebot web

Greenvar's thing worked, but it broke the API. Add a new function "preview45", so everything that referenced previewer.preview and whatever still worked. It might not be as robust, but it works and will get the functionality into somebot so we can find what breaks.

This definitely isn't as nice, because the texture pack needs to be broken into sprites, rather than using a flat png, but for the moment this might be acceptable. Someone could make a script that takes in a texture pack and outputs the correct sprites if the sprite-route is the correct way to go.