Add lugs on camera platform to set PCB direction

Following on from #432 (closed) (#432 (comment 2742885624))

Consider adding lugs outside the posts on the Pi Camera platform for the low-cost optics, so that the camera can only be placed one way round.

This mock-up was created by adding in picamera2.scad:
In module picamera_2_bottom_mounting_posts()

        if(outers){
            difference(){
                at_picamera_2_extra_post_size_pattern(){
                    cylinder(r1=r1, r2=r2, h=h+1, $fn=12);
                }
                rotate_z(45){
                    translate_z(h+1){
                        \\ this cube is a dummy for the Pi Camera PCB                        cube([picamera_2_hole_spacing()+4,25+4,2],center=true);
                    }
                }
            }
        }

and a new module

module at_picamera_2_extra_post_size_pattern(){
    screw_x = picamera_2_hole_spacing()/2;
    rotate(45){
        reflect_x(){
            for(y=[0,13.5]){
                translate([screw_x+1, y, 0]){
                    children();
                }
            }
        }
    }
}

The optics fitting dovetail wedge does not allow for a good lug at that corner, but the others should be sufficient.