Robo3D Low Profile fan duct mount with support

A remix of thing:431160 that adds support so it will print properly using the default MatterControl software that comes with the Robo3D R1 printer. Even if you enable "generate support material" in MatterControl it seems to think it's not needed (under default configuration, at least) and so this design lets you print it regardless.

This replaces the bracket from thing:431160 and works with the original duct.

The supports are a little thicker than normal but can be removed with a hobby kn