Added model group support, you can now have multiple meshes in one export.
Removed OBJ and mesh replace export options.
Mesh replace didn't work, might get added again in the feature.
OBJ needs to be rewritten as well to support the multiple meshes, and Unity now has model export options in engine.
Version 1.8.0+ is now only supports Unity2018.3+.
Moved/changed replace OBJ to ReplaceMesh.
Optional model/texture/material export.
Added Material export option, set shader and shader properties to assign exported textures.
Added Prefab export option, exports mesh as an Unity .asset file and creates a prefab to link it to the mesh filter/renderer, added the option for auto assignment of the exported material (New default).
Bugfix texture export: where textures regarding of their settings would be exported as sprites.
Update texture export: original textures will now be copied to get the pixel values with the correct import settings applied to prevent strange-looking normal maps and color changes.
Folder creation: the required folders will now be created by the tool, no need anymore to save empty folders.
Minor changes: Renamed some variables, testing a new layout error fix, started working on material export.
