LimeSDR Mini case (remix)

Added arrows to the top case (named bottom for some reason) to show which SMA is TX and RX.

Also recessed the nut head's a bit more, so the nuts are fully recessed and the head of the bolt is better hidden.

Removed the vents (cause they don't do much tbh), so now you can have a flat surface to emboss anything you want, and also removed some of the shroud over the USB port as it was a bit too close to plugging it in to the laptop, so there's some space now.