Parametric diffuser for LED strips.

Parameters (in milimeters) :

• `length` - length of LED strip you want to cover (in my case, 50mm per segment)
• `width` - width of the LED strip (usually around 10mm)
• `height` - height of the LED strip, with diodes (in my case - 2mm)
• `thickness` - thickness of the diffuser to be
• `spacing` - distance between LED strip and the diffuser
• `close_front` - should it have closing lid in the front (true/false)
• `close_back` - should it have closing lid in the back (true/false)