How to write proper e57 header

Hi all. Due to lack of extensive docs and tutorials, I cannot find a way to properly specify the e57 header which would be accepted by external tools such as Autodesk ReCap.

```
Data3D scanHeader;
scanHeader.guid = "{D3817EC3-A3DD-4a81-9EF5-2FFD0EC91D5A}";
scanHeader.name = ustring("merged_scan");
scanHeader.pointCount = N;
scanHeader.pointFields.cartesianXField = true;
scanHeader.pointFields.cartesianYField = true;
scanHeader.pointFields.cartesianZField = true;
scanHeader.pose = RigidBodyTransform::identity();
scanHeader.cartesianBounds.xMinimum = minX;
scanHeader.cartesianBounds.xMaximum = maxX;
scanHeader.cartesianBounds.yMinimum = minY;
scanHeader.cartesianBounds.yMaximum = maxY;
scanHeader.cartesianBounds.zMinimum = minZ;
scanHeader.cartesianBounds.zMaximum = maxZ;
```

While this works (i.e. I manage to save e57 when using this header), I have issues opening this with eg. Autodesk ReCap. Are there some fields that are usually required to be also filled? Or is something not filled properly here? Would appreciate any advice.

No repository file or test is named. Start by reviewing the E57 header requirements and the Data3D fields shown in issue #323, then reproduce the saved file with Autodesk ReCap. Done means documenting the required fields and providing a reproducible valid header example.

Written by the indexing model from the issue text.