OpenForge 2.0 Sewer Deep Sluice

Hi all! The [OpenForge Sewer collection](https://www.thingiverse.com/devonjones/collections/3871473/things) by @devonjones looked like a lot of fun to paint, and @Poxos has a great [OpenForge 2.0 version](https://www.thingiverse.com/thing:3551914) of the walls and shallow sluices, but I wasn't able to find a 2.0 compatible version of the [deep sluices](https://www.thingiverse.com/thing:988413), so I pulled them into Blender and reformatted them a bit to fit better. I also included @Sancharizard's [straight sluice transition](https://www.thingiverse.com/thing:4851261) so that I could get them all to be more or less flush.

In order to fit in the vertical space but preserve the detail on the stonework, the bottoms get pretty thin. I printed these with 0.1mm layers in normal PLA and there's enough give that they never felt at real risk of breaking. Using 0.1 gets 2–3 layers crosshatched over each other, which helps. The cross is definitely the worst, and everything else has enough struc