Mini panel voltmeter

A panel mount housing for the small import LED voltmeter modules. The back of the case is a tight fit which retains the module without any screws, but there are also holes for small self tapping screws if you don't want the rear enclosed.

There are now two variants:
1) The original simpler design that can be retained in a panel by either gluing or via a simple friction fit retention clip
2) A newer design that uses M3 screws to pull the bezel tight into the panel. This requires printing two of the threaded retainer parts and they need to be fitted into the side of the main body after it has been fitted to the panel. This provides a more secure retention.
Both designs use the same rear panel.

Improvements over the original model from Arezus:
Removed the tiny pillars that retain the rear panel. I found these snap if you so much as look at them hard.
Reduced total depth as the rear panel fits flush with the back of the housing.
The module now fits more tightly up the bezel, the ori