VESA Base nonuts

Just a small mod to the VESA base. I removed the nut pockets and tightened the holes up to 2.8mm so a 3mm screw should thread itself in fine. This will lessen the need to have an exactly precise screw length. For me personally I've found 3mm screws threaded into a 2mm hole in PLA to be plenty strong for items like this. I also tightened up the mounting holes for the Pi a very small amount (~0.1mm) to better fit the plastic retention pegs I'm using. I made these pass all the way through so the pegs can be pushed back out from the bottom instead of having to grip them with pliers so near the Pi.