Fixed vegetation wind effect on billboards.
Added unlit vegetation technique & example material.
Added alphamasked variation to Unlit shader.
Fixed billboard textures displayed upside down. Note: this is a breaking change for old scene content that manually specifies non-default billboard UV:s.


git-svn-id: http://urho3d.googlecode.com/svn/trunk@2688 3bd170d8-ddcf-f82c-f583-7a401ccf5608