More default settings in model viewer

[xtom]

I really like setting the new physics options in the model viewer and it really helps streamline the process of placing models into the level. I was thinking it might be good to also be able to set other default settings for a model in the viewer such as nav obstacle, collision type etc, so you wouldn't have to change them each time you drag in another copy of the model into the level. But keep the existing settings too so you can change/overide them on different instances if you need to.