enabling mip filters for models with textures

[johanos]

I found a bug with models that use large textures,
as you can see, we start to get kinda gross aliasing when you move away from the camera

this is due to not having enabled any mip filtering since when you create an SCNMaterialProperty, it defaults to none. to fix this we simply have to enable linear mip filtering

the only downside is a performance hit because we were doing no calculations to some calculations, however this shouldn't be too bad of an issue

Before:

After:

[magicien]

Great! Thank you for your contribution!
I've been slightly busy recently, but I'm going to check it soon!