Request : Add trees and road in building mod

```
We all know that perfect space efficency building is completely messed up by
rocks.

So, could you add 'tree' building and maybe 'road', only for esthetic?

The original game had a picture with trees on its cover. It was a lie. Maybe
also a very low morale bonus when tree are built on a planet. Who would enjoy
living on a planet without plants?

Obviously, this sugestion has a very low priority if accepted.
```

Original issue reported on code.google.com by `benjamin...@gmail.com` on 27 Jan 2014 at 6:02