Fix growing zone for 1.1, allow cactus on sand

[meiskam]

I know this isn't a proper edit, but it's the best I can do (the code actually kinda works, no matter how hacky it looks :P). I'm sure you know your codebase and Rimworld's much better than I do, and can fix this properly.

With 1.1 you can now plant SaguaroCactus, which has a min fertility rate of 0.05. Vanilla by default hasn't added the ability to place a grow zone on sand yet. I thought your Enhancements mod was a great place to fix this oversight.

[alextd]

Hmm maybe the base growing zine should just be allowed on sand, and default to cactus, which this “match” zone tool will just inherit.

Of course you usually don’t want to extend a growing zone into sand.

So this is something to think about before making a change. I am currently on a couch with a cat on my lap, soo, later