Waterproof forumslader housing

Update 25. Jun. 2021: fixed bug with only the sides rounded; this is also default now for better printing


Description:
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This is a waterproof housing for the [forumslader](http://www.forumslader.de/automatiklader/), a device to charge your USB device with the hub dynamo of your bike in a very efficient way. The example is fitted for the 2.9Ah version with three LiMn 18650 batteries. It is fully parameterized, so you can adapt it to other versions. I added a dovetail joint for