Support IFC file format

[HuguesDelorme]

Implement support of IFC files in Mayo for import/export

https://en.wikipedia.org/wiki/Industry_Foundation_Classes
http://www.ifcopenshell.org
https://github.com/ifcquery/ifcplusplus
https://wiki.freecadweb.org/IfcPlusPlus
https://wiki.freecadweb.org/IfcOpenShell

[Mannshoch]

I would really like that feature.

Optional:
May a bit different approach would be nice here. (may could be nice in other file types to)

1. Export selected items -> IFC
2. The model tree change to an IFC tree.
   UI:
   • OK / Cancel
   • Project:
     • Site:
       • Building:
         • Storey:
           // Right-click create a new Assembly.
           // Drag and drop bodies like in a file-browser
           // Slow double-click or F2 to rename a Body
           // On Right click you could choose if a body should be saved as tessellation data only or as geometrical data.
           // Click OK to save this IFC