Duplo compatible straight track with elevation adjustment

This track can be used to change elevation based on your need. I remixed @pjotrx's design, adjusted a few things to make it easier to print (first layer "brim" for stickines, middle piece bridging fix), and added an ability to configure custom elevation. Rendered 0 elevation, half brick (9.6mm),, and full brick (19.2mm) elevated track. When installing, snap appropriate height brick to the straight piece, as in my picture.

Pull requests welcome :) https://github.com/sergesyrota/duplo-elevated-