Fixed Wall Mount C-Clamp with updated screw handle

As reported by user mrstoned on the comment section of Wall Mount C-Clamp by Gophergames the meshes of the clamp and screw knob had some erros on it so I fixed them using Thinker Cad and also created a new version of the screw with two variations of size of the knob based on the elipse version of Remix of G-Clamp with updated screw handle by Martusha