Please add the ability to crop ground object after importing

[jforbess]

Hi, I have just started exploring the use of the topography data that is now available as an import as part of the interactive map in the 3d shade scene. It's great. 

But it would be very helpful to be able to crop the ground object, since I am usually modeling large projects, and sometimes they run more north/south, as a portrait aspect ratio, while the download is always a very wide landscape aspect ratio. 

Thanks!