Upgrade to net7.0

Upgrade to .NET 6.0

.NET Core version has been upgraded to 3.1

MetaModel struct is extended with author, date of creation, schema, creating application.

Adding related objects of spatial elements. For example IfcMember, IfcPlate.

Fixing elements with null parents in JSON metadata bug.

Update xbim to support Ifc4 file format.

Fixing async issue which might cause the json output to be truncated.

This initial release is for testing out the full workflow and usage with xeokit.

• CLI
• Support for IFC 2x3
• Multi-platform