Changed merging of texture color and color for billboard

Signed-off-by: Markus Tillman <reetopps6@hotmail.com>
Merge branch 'master' of https://github.com/Malow/NDYGFX
Moved rendering of invisible objects to a later stage to include skybox and fog for invisibility.

Signed-off-by: Markus Tillman <reetopps6@hotmail.com>