RPLIDAR A2 Base

Base for RPLIDAR A2.
Raises the RPLIDAR 46mm to allow it to scan over other objects mounted to the same surface that are less than approximately 70mm tall.

All mounting holes are sized for M3 machine screws.
RPLIDAR mounting holes are designed for M3x8's without washers.

UPDATE 190501: Added RPLIDAR_A2_mount_56mm.stl, which is 10mm taller than the original version and increases the protrusion of the RPLIDAR mounting screws by 0.4mm.