Customizable RC car battery post

Fully parametric (customizable) battery post for RC cars. 2018-05-19: added cross base version. **Parameters** POST_DIAMETER,POST_HEIGHT = diameter and height of the cylinder. BASE_WIDTH,BASE_HEIGHT = base width (excluding cylinder base) and height. SCREW_DIAMETER, SCREW_LENGTH = diameter and length of mounting screw. PIN_DIAMETER = diameter of the pin hole. PIN_STEPPING = distance between pin holes. CROSS_WIDTH, CROSS_HEIGHT, CROSS_THICKNESS = parameters for cross talus.