ImportStep does not respect unit

[Steinblock]

I have a simple step file and CADability shows the width and height as 0.38 and 0.8.

However the part has been constructed in Autodesk Inventor 2023 and saved with unit meter. Other step viewers show the correct size of 380 and 800.

Here is the file for reference.

simple-part-mm.zip

[dsn27]

It seems like the unit is not read under all circumstances.
While there is code that is trying to figure out the units, this does not seem to work for this file.
e.g.
https://github.com/SOFAgh/CADability/blob/e6794d6730d618307e2a8d8c5f34f6fbe7d97719/CADability/ImportStep.cs#L4757-L4782

https://github.com/SOFAgh/CADability/blob/e6794d6730d618307e2a8d8c5f34f6fbe7d97719/CADability/ImportStep.cs#L4804-L4825

[dsn27]

The original code is looking for "conversion_factor" and "value_component" inside a Units Items.

But it looks like in issue153.stp the unit is available at top level and we just need to read it.

Remarks:
We should add support for other Units and check the old code.
Why is the factor always multiplied by 1000?
What happens if this code is called multiple times?

https://github.com/SOFAgh/CADability/blob/e6794d6730d618307e2a8d8c5f34f6fbe7d97719/CADability/ImportStep.cs#L4819-L4820

We would need several STEP files that trigger this code path to check on this.

[dsn27]

Closed by #182