Added ShapeBuilder class and library for non structural assets (

`ShapeBuilder` class is used to programmatically create 2d and 3d ifc shapes and representations. It's inspired by the way OpenSCAD language is designed - the goal was to create a readable and easy way to create new shapes. The class can be imported from `ifcopenshell.util.representation` module.

Examples of things created with `ShapeBuilder` can be found in `shape_builder_examples.py` or `generate_furniture_library.py` / `Non_structural_assets_library.ifc`.

Also added ifc library of non structual assets (furniture etc) - `Non_structural_assets_library.ifc`. All assets are using most common dimensions for them - it makes it good for prototyping. Related to https://community.osarch.org/discussion/1192

src/blenderbim/scripts/generate_steel_profiles_library.py

@@ -90,15 +90,15 @@ def create_simple_2dcurve(coords, fillets, fillet_radius, closed=True, ifc_file=
     ifc_curve = None
     if ifc_file:
         ifc_points = ifc_file.createIfcCartesianPointList2D(points)
-        ifc_segements = []
+        ifc_segments = []
         for segment in segments:
             segment = [i+1 for i in segment]
             if len(segment) == 2:
-                ifc_segements.append( ifc_file.createIfcLineIndex( segment ))
+                ifc_segments.append( ifc_file.createIfcLineIndex( segment ))
             elif len(segment) == 3:
-                ifc_segements.append( ifc_file.createIfcArcIndex( segment ))
+                ifc_segments.append( ifc_file.createIfcArcIndex( segment ))
 
-        ifc_curve = ifc_file.createIfcIndexedPolyCurve(Points=ifc_points, Segments=ifc_segements)
+        ifc_curve = ifc_file.createIfcIndexedPolyCurve(Points=ifc_points, Segments=ifc_segments)
 
     return (points, segments, ifc_curve)