Improved hot-end platform for 3DR Simple

This is an improved hot-end platform for the 3DR Simple 3D printer.

Features:

• Modeled entirely in OpenSCAD.
• Captive bolts to make tightening easier.
• Compatible with parts designed for the original 3DR micro platform, including fans.
• Compatible with parts designed for the 3DR Simple micro platform, which has a different bolt arrangement.
• Low-profile height (8mm)
• Optional integrated mount for an inductive bed sensor.

Works great with this E3D mount.