Model silo_top001+ 1.0

[Tumby]

silo_top001+ - Edit of props_mining/silo_top001.mdl

The following things are different from the original:

1. There is a collision model.
   
2. The texture is slightly more detailed.
3. The prop is seperated into "base" and "railings".
4. There is a flat version of the base, for special cases.