Parametric Syringe V1

I needed a syringe for injecting resin into a tiny mold. carlesoriol's syringe was true to the typical syringe design, but not very printable. This one fixes that.

Note: the .STL files are included here as examples. Some of them lag are actually outdated compared to the OpenSCAD file. It's better if you create your own STLs through the Customizer.

List of changes
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* better spacing for display modes
* fixed display mode rendering issues
* fixed non-manifold surfaces
* made nozzle length customizable
* added ability to render individual parts
* modified for supportless FDM printing
* changed default scale to mm (was cm)
* added "part" option for automatic Customizer generation

I'm not yet satisfied with how the "piston" attaches to the "plunger". Share your thoughts, please!

If you need more customization or need one printed, let me know.