Rock/Dirt generation code, ant slowdown through harder dirt, and a few fixes too

Pretty horrible code for making the rocks/dirt patterns. It's also pretty slow, it tends to take a few seconds to generate the level now with the current settings. Feel free to discard this part of the pull request if you can do a better job.

There's also code to slow down the ants in harder dirt, and then a couple of fixes in the TileInfo stuff.

Also added in some code for multi-colored soil. Looks good!
![antstuff](https://cloud.githubusercontent.com/assets/1606277/5335674/7c838952-7e74-11e4-8d39-fd0d3de7f94a.png)