Customizable 7-segment display diffuser

Revised SCAD code with additions and minor modifications.
Tested in OpenSCAD version 2019.05.
Requires utils/build_plate.scad and write/Write.scad.

Apparently Customizer isn't working [anymore](https://www.thingiverse.com/app:22/comments), but the missing files can be downloaded from Thingiverse: e.g. [here](https://www.thingiverse.com/thing:16193) and [here](https://www.thingiverse.com/thing:44094) and then put in a libraries folder below the folder that has the design file (customizable_7-segment_mx.scad).

Modifications by Maxint (20190903):
- added segment-end margin
- added segment styles (angular, rounded)
- rectangular hole for SMD-LEDs (two sizes)

Note 1: the included stl file is only provided as an example.
Note 2: Especially for SMD: the LED holes may need manual cleanup as no internal support is generated.

Tip: increase the segment-end margin if segments collide. This decreases the length of a segment.