D2R lower resolution `.model` files

[pairofdocs]

Hi Norbyte,

Thanks for your work on LSLib!

I ran into an issue with D2R .model files-- I was failing to load the lower resolution models (*_lod1.model, *_lod2.model, ... ) with LSLib.Granny.GR2Utils.LoadModel(modelpath);

(https://github.com/pairofdocs/Unity-D2R-Scene-Editor/blob/master/Scripts/SaveJson.cs#L54)

The higher res *_lod0.model files loaded correctly.

If you have free time, can you please take a look? I'll zip an example folder with a full set of D2R model files.

act1_town_tents.zip