New trees test

This is a test with a new tree model from Polypixel3D.com.

I'm in the process of replacing all the foliage models. This one looks good, but isn't optimised, 8000 triangles for the LOD0 and 3 materials. It's difficult to mantain the 60 fps.

Each material is a aditional drawcall, so I'm going to try to reduce to 2 materials or one (using alpha masks).