Downscale all vbuildings 50%, redo normals and add a specular map
partial patch to reduce the grid effect described in #1631

This doesn't fix the problem, it just reduces the effect.
remove luamodelviewer
Merge remote-tracking branch 'luomu/downscale-buildings'
Merge remote-tracking branch 'johnbartholomew/issue-1631-fog-grid'