Bren: 3D Guns

I enjoy the mod [Bren](https://modrinth.com/mod/bren) by sniffiandros, but felt it could be improved with 3D models for its guns.  Included are custom 3D models of the Auto Gun, Machine Gun, Revolver, Rifle, and Shotgun; as well as their Netherite versions. Variations to account for magazines and clothed magazines are also included. The clothed magazine remains dyable as well. Models and textures created in Blockbench