Arduino / NodeMCU alarm case (Remix)

This is a remix of the case from donsas. After printing, I noticed a few things I would like to have different.

I built the whole model in Freecad from scratch and adapted the following things to it:

- The holding columns are now a bit shorter so you can tighten the case better.
- The holder for the display is no longer a slot (it was blocked in the original) but a mounting plate. It also has a cutout for the heightening on the board of the display.
- I omitted the recess at the front fo