Customizable train tracks, optional with elevation adjustment

With this customizer, you have one place creating most common tracks and small bridges, both straight & curved.

Why another duplo track customizer?
It's based on the "[building block interface](https://www.thingiverse.com/thing:2952203)" module. First use this module to calibrate simple interfacing geometry. When you are satisfied, you now could print tracks from this train track generator & have one stop for most tracks you could think about, without loosing filament by tuning whole new parts over and over. This train track generator needs also the awesome [dotSCAD](https://github.com/JustinSDK/dotSCAD) library.

Options:
* Generate long or short straight/curved tracks.
* Create curved tracks with a different radius, so these could be placed next to the other tracks.
* Create small bridges/ramps.

Some considerations:
* STL files for download, are generated for using 0.8 nozzle & 0.2 mm layer height. I would recommend to **first print the calibration blocks** and **then r