Allit EuroPlus Flex 37-15 organizer boxes

Changelog:
2018-10-16: I updated the small middle boxes with a slightly smaller outline of 59,5mm x 30,0mm, according to baryluk's comment.

Replaces the front box of an [Allit EuroPlus Flex 37-15 organizer](https://www.qwant.com/?q=Allit%20EuroPlus%20Flex%2037-15%20organizer%20457202&t=images) (order no. 457202) with six separate boxes, which allows to take them out individually.

You'll need to print two of each size for one organizer. If you want the lid to shut tightly, you'll need to m