Effects/model-default.eff move skydome to technique 5 to provide more headroom

Effects/model-default.eff move skydome to technique 5 to provide more headroom
Effects/model-combined.eff fix techniques numbering. Make active under rembrandt too. add model-combined-deferred as a stub for now for specific
Rembrandt use.
Users of model-combined with normalmaps should change the technique number to 9, and duplicate that entry for technique 8.
Fix some longstanding png warnings. Provide null_reflectdir.png for model-combined
This should fix part of bug #726
Signed-off-by: Emilian Huminiuc <emilianh@gmail.com>